ok i'm in high school and there is this hb9 in my class, actually she is a severe case of one itis.
i've been in class with her about 5 months now, way too long i know.
but i just didn't know what to do because i couldn't read her, i wasn't sure if she was into me. I feel like a total afc, cus now when i look back at all the ioi's i got and all the kino i had going i realize i should have closed her a long time ago. but she has allways been like she wanted me to chase her, for example she would give a huge ioi, we had a nice conversation or something, and the next day she would act like it never happened.
i guess i waited too long so the attraction just kind of faded away.
the problem is that i can still see some signs now and then, she does what she have allways done, one day i catch her staring at me and then there is nothing, maybe the next week it happens again, and then something else.
or for example last week we were some friends talking in class and it came up that my birthday is in two weeks and then the hb9 was just telling me "i'm coming to your birthday party" and im trying to act cool with some pua shit. looked at her and was like "who said you were invited?" and then nothing, don't think she bothered to answer she just smiled at me. what the hell i've never said anything about a birthday party

ANYWAY. this girl is cool with me, the ioi's are going up and down all the time, what should i do?
and my birthday is coming up so any good lines about that?

I think you just need to relax, you seem to be very nervous about this situation, when really it has presented itself on a lovely plate for you, this girl is clearly interested in you, so why not just talk to her? The tips and methods in your typical PUA book/guide will tell you how to get this girl attracted to you etc, however, if this is already the case then you don't need to read up on that.

If this girl is already attracted to you then just be yourself, things will escalate naturally this way, you say you have had some nice conversations etc with her, so why change this? It sounds to me like this is an opportunity waiting for you to just take it, grab that bull by the horns!

As for bringing your birthday up, are you having a party? You said you haven't mentioned anything about it, if she said she is coming this was basically just her flirting with you, you responded well to this rather than jumping through her hoops and coming out with something AFC like "I would never not invite you" etc. So well done with that.

May I ask how old you are? As school to me is 16 or younger, if this is the case then why not just tell her straight, for example, if you have no party planned just tell her you are doing something with family, but wouldn't mind letting her treat you to a coffee/cinema/dinner (change according to age suitable) for a belated present, however, if she says no, don't make a big deal out of it, just brush it off and continue with what you are doing, as if it never happened.

- SC

Thanks for the advice Second Chance, appreciated