Was I right to be upset about this?

[Madame Mommy Chaos]

(Just a reminder: I report ALL answers that complain about my question being too long or say TLDR)

As the middle child of my family, I have a younger sister who is going through her teenage phase, which I am not too far removed from. Therefore, I try to help her and I try to give her advice and spend time with her the way that our mom has never spent time with us.

However, she has been taking advantage as of late. My sister is increasingly more disrespectful and rude and now has a sense of entitlement that permeates the air whenever she walks in. My family is important to me, which is why I like to go out of my way to help my sister when I can and give her guidance when I think she needs it. Lately, this has been backfiring on me. When I go out to buy her things, I give her a limit on what she can spend and she goes over that limit every single time and I get chewed out by my parents for not having leeway. So even though she doesn't get what she asked for, she still wins that battle every time because my parents are reinforcing her.

I went out recently and bought her over 100 dollars's worth in clothes and shoes and Bath&Body products that I really shouldn't have spent my time with. I did it because I hadn't had the chance to buy her a Christmas gift on time. This morning, we went out to breakfast and I bought her a couple of movies and paid for some food for her and spent my money and my gas to get her around. Now before you lecture me about taking her out of school, don't. I hadn't seen her in more than a month and this was possibly the only time I would see her again for another month. While we were out, she put more things in the cart than I was planning to buy, so I told her to put it back. She responded that it was only - dollars and then got mad when I stood firm. After that, she tried to put a pair of shoes in the cart that I also did not want to buy, and then got mad about that. I didn't think much about it at the time.

I come back home to find that not only has my sister NOT thanked me for any of it, but she has also taken to TWITTER to tell people how embarrassed she is to be around me and that she gets annoyed when she is with me. It made me so angry that I cried. My fiance has suggested that I take all of her items back to the store and make her pay me back for the gasoline I used to take her around.

My parents say that I am taking this situation ENTIRELY too seriously, but it feels like a spit in my face. I have been sick for the past week and took out my time to help her and this was the thanks I got. Am I right to be mad about this? What should I do?

What I have been considering is just cutting her off all together and not bothering to come back to visit when I get married and move to CA.
They aren't "gifts." I buy her things that I perceive that she needs. The money I spent recently was for her Christmas, and so that WAS a gift. Today was really just clothes/bra shopping.

I don't do it for validation, I do it because my mom won't.

[Curley Fries]

I would return the items and tell her that you have to earn things, and since she was not respectful she does deserve what you bought her. Then she might realize that she was being disrespectful.

[Lor Gal]

I'm confused. It's seems like you're buying her gifts. If you want to buy her a gift, don't take her shopping with you. And, you are looking for some sort of validation (in the form of gratefulness) for your gift giving.
Perhaps, what you need to be doing, is asking yourself WHY you are buying her all this stuff. And, what exactly are your expectations. It sounds like you are hurt and angry because whatever your "expectations" are, they are NOT being met. I think you are investing too much into this relationship.
What's done is done. Now, take a step back. Take a few deep breaths.
Take a different approach. Stop buying these gifts.
Be kind, but remove yourself emotionally from her drama. She can not take advantage of you unless YOU ALLOW HER TOO. Stop giving her so much power. And don;t continue to play this victim role that you find yourself in.

[Mary]

Newsflash: YOUR SISTER IS A SPOILED BRAT.

Yes you have the right to be upset, but I'm sorry to say that you went overboard by buying her all that stuff in the first place. A simple birthday gift that you picked out would have been good enough. Taking her out of school just to go shopping?--all because you didnt want to wait 4 weeks to see her?? Dont you realize that you went totally overboard in spoiling that kid. Stop spoiling her. And yes she was a little brat to go on twitter and say such nasty things about you to the entire world. Sorry, but she's acting like an ungrateful little bit@# (excuse my french)...Here's what you should do--Stop buying her things. Tell her that if she ever talks about you online again you're going to kick her little ungrateful a$$ (but dont really do it, just threaten her with it), and then stop calling her for the next few months. Put some space between you and focus on your life. And your parents are just enabling her and allowing her to be a disrespectful little brat. They say you're taking this too seriously--Really? She bashes you on twitter and you buy her the world, and you're overreacting--Really?? I guess your parents think her behavior is cute. But I dont. Its ugly.

Anyway, your sister is a brat. And yes, I agree that if you can, take the items back to the store (if she didnt open them yet). But dont ask her for the gas money, but I'd love to see her face when she comes home and sees those items gone--Priceless! LOL. Now thats some sweet revenge. Hey, go to her room when she's not home and get them (dont get them when she's home because your parents will side with her--and dont even tell your parents anway, its your money)

Dont give her a damn dime anymore, and dont even buy her so much as 99cent toothbrush from the dollar store if she asks for it. Just calmly say, "nope, you're too embarssed to be seen with me, sorry". Good Luck

[Maineruano]

You're very right to be upset.
Don't give her any more things.
Spend time with her, but don't be buying her gifts.
If you want to take her to the movies, great.
If you want to buy her lunch, great.
But if she wants presents she has to bring her own money.