sorority gpa

Most sororities do have a higher grade requirement than the minimum needed to rush. Many of the "cuts" made after open house round are purely for GPA reasons, to have the most options in recruitment you need a 2.8 or higher really. Every sorority has some sort of cutoff where if you're below it they'd consider you a grade risk and it's important for them to keep up their chapter/new member GPA

I'd still encourage you to rush and see what happens anyway, and you can always work on getting your grades up the next two semesters and rushing next year if it doesn't work out!

Your options across the board are definitely more limited having only a 2.55. If it comes down to you and another girl who is exactly like you except she has 3.0, heck even a 2.8...they're probably going to take that girl over you. Sorry, just being honest. There are hundreds of girls rushing and we HAVE to cut a certain number of them each round.
If those are the only 2 you are interested in well, good luck then. You're setting yourself up for disappointment only being interested in. And I can tell you right now there are definitely a few chapters who wont even care how social and fun you are with that GPA. ADPi, Theta, Gamma Phi Beta and AZD to name a few. You can probably count Pi phi in there too since they are still so new and have nationals floating over them so hard.
Personally I know that Phi Sig and DG have both taken girls with GPAs 2.5-2.7. Maybe others have but from my experience, those 2 definitely have taken girls with those GPAs.

If you have below a 2.75, most will drop you right away unless they literally love you like if you know a bunch of girls in the sorority, or unless your a legacy.

What happens if your gpa is lower than a 2.5 at the end of freshman year are you kicked out of the sorority you just joined??

honestly the only top tier that might take you is sk. as others have said, phi sig may take you, maybe even asa too, and dg definitely will. only having your sights set on a top tier never ends well for anyone though.