Why do i keep getting jealous of other people's happiness? are they really happy?

[Katniss]

I only get jealous of people's genuine happiness, not people who pretend or try to act happy. There is this person i follow on twitter, she is my role model, my idol, she seems to be the happiest person in the world. she is very friendly, sweet and very beautiful. she has great family, friends and a bf. she has everything. Everytime she is very joyful i get really jealous. not a sign of stress or depression from her face or body language. i get so jealous and wish i was her. When she does have problems as i can see from her twitter/facebook it makes me feel better. but the problems are so little. the thing is that she always says how thankful or special she is the life god has given her. she always says something similar to that like every week. this is making me really angry kinda, what if she is lying? i read a story about a guy who had everything in the outside, everyone thought he was the happiest guy in the world, in the end he commited suicide because he was so empty inside. do you think she is empty inside? why would someone keep saying how perfect and lucky their life is? i really look up to this person for her happiness, but in the same time jealous and wonder if maybe she is lying. i am all over the place, i love and hate her!
but i really look up to her, that's the thing. and i am very happy for her. i'm not a rude person. i just...i really dont know. i just wish i had a life like her. i am not going to do anything rude. i am just sad that i wish i had her life. i am happy that she has a good life. i really dont know whats wrong with me, thats why im asking this question