Crush Will Be At Party, Need Help!

For most of my life, I was not a person who socialized with people a lot. It wasn’t until my sophomore year in high school where I slowly started to talk to other people because of one of my friends. Although this friend helped me to talk more, I still have problems socializing with people I meet and I struggle trying to join in on conversations, but I was still able to make some new friends for the rest of my high school years. In my senior year of high school, I added Spanish to my schedule days after the school year began and my teacher sat me behind this cute girl who was a junior. She and I talked a couple times before we switched seats later that week. I didn’t know it then but a few months later I would develop feelings for her. This girl is the embodiment of my perfect girl. Sadly, I didn’t really talk to her that much after we moved seats but one of my friends since junior year did. This friend of mine was a sophomore during my senior and we met the year prior. Without doing anything about my feelings for her, graduation came by and she turned out to be my last high school crush. I now go to a community college that is closer to my house than my high school was and my friend who talked to my high school crush still texts me. I tried to move on from this girl, but at my community college, there’s no one there that compares to her. A couple days ago, my friend texted me that he’s having this party at his house where a bunch of his friends will attend. Turns out one of those people is my crush. What do I do if I see her at the party and how do I go up to talk to her? What if she’s talking with someone or with a group of people?What do I talk to her about since we rarely talked in that class and how do I ask for her number without getting rejected?