Why would a seemingly straight girl date an obvious gay guy?

[erthtrh]

Hi. Okay, so it's been half a year since she rejected me and I still can't seem to get over her. We became sort of friendly and once went out in a club with our mutual friend, but when I asked her to go out she started making excuses so I directly asked her if she's interested in me and she replied (suprise!) no. I've never been in a relationship before (I'm 18) and neither has she. I also wanted to mention that I found her on twitter and I read her posts (I'm not stalker, just curious lol) from which I've learned that she was a long period of time in a love with another guy from school who is in a relationship, so she regularly took to twitter to write about her pain and bla bla stuff. On twitter she has only few friends from school and it's mainly like her "diary" sorta thing (you can't find her by her real name, ofc) so I also learned that she never wrote a single tweet about me and it just confirmed that she doesn't give a **** about me. The things got worse when she started dating another guy from school who is clearly gay (there's no doubt about it: he behaves like a black soul diva and his idol is Beyonce). He's overweight and really self-absorbed (sorry if I come off as a jerk, but I'm just stating the facts here). Not that there's anything wrong with that, but he's just that kind of guy that is so obviously feminine that I just can't get how could any girl (let alone that attractive girl) be attracted to him. The funny thing is that on twitter she doesn't mention anything about her being in love or him in particular. His parents are pretty rich and I guess that because of that a lot of girls want to be his friend and gravitate toward him who is basically repugnant to almost everyone else I know. Now, I know that it's not something I should worry about and that I shouldn't have interest in her anymore, but I'm starting to wonder is that a reason why they are in a so-called "relationship". Our mutual friend that I mentioned is an out lesbian and she used to be her best friend. They took me to a very gay-friendly place and she didn't seem to care about it. I don't know how common is for a straight girl to be really close to a lesbian that was very open and vocal about her being horny and checking on a lot of girls that night. I'm not judgmental type of person and I don't mind her being gay, but I suspected that my crush was also gay which doesn't seem logical now that I've read her tweets about her having a crush on a guy from the school. Know some similar situations, "couples"? Any thoughts about that, I would say very strange girl that I happened to have a crush on. Thanks.
I just wanted to add, in case I wasn't clear, that she only had a crush on that guy from the school and she was never in a relationship before this one (with the guy I didn't describe complimentary).

[Patrick4024]

Maybe he is a challenge to her, and she wants to try and change him.

[MzCalypso]

She doesn't like you and she does like him, and you saying his is an "obvious gay guy" sounds like dog-in-the-manger jealousy.

She rejected you, man up and accept that. And dump the racist nonsense, too.

"I'm not judgmental type of person and I don't mind her being gay,"

Yes you are, and yes you do. She has rejected you, but you keep assuming that you have the right to make judgments about her sexuality and the people with whom she chooses to associate.

It's over, erththr. She's not interested. Move on and find someone who wants you back.

Oh, and stop stalking her on Twitter. You're only aggravating yourself.

[Binary]

I'm really not sure what to say as I have never dated before either; I'm thinking that maybe she's a closeted lesbian or bi (just a thought so don't stone me lol)... from what I can understand from your description,maybe she and her new boyfriend decided to become beards (more info here: http://en.wikipedia.org/wiki/Beard_%28companion%29)... also the way you stated your questions about your crush being "seemingly" straight shows that you suspect she's gay too... the way you described her boyfriend was quite stereotypical, i know a very very straight guy whose idol is Lady Gaga but I understand that you wanted to give us an idea of what you mean so I don't take it to heart. Another thing may be to talk to any mutual guy friends that know her (someone who will not start snitching on you at the drop of a hat) and ask for their opinion. I hope you find answers