Today I got a big crush on another girl and idk what to do. What do you feel about it?

Today I had some classes in another institute and there some very beautiful girl came. I had been seeing her since I joined the institute a month ago for some courses but today she literally sat beside me because there were no other empty seats. She is actually my senior as she graduated college and is working now but she is attending classes for preparing for exams to get into grad school. So she is 23 or 24 and I am 21 in last year of college and I got an instant crush on her. She is too beautiful. She was sitting beside me and something was happening in my stomach and my heartbeat was rising. She looked so pretty wearing her jeans and pink dress and she also wears glasses just like me . But I am too shy so I never initiated any conversation with her. She did talk a bit with me asking which class we have next and stuffs and I answered her and thats it. Her voice is too sweet and I was kinda getting butterflies in my stomach after hearing her sweet voice. Sadly nothing much happened because I am too shy. I already have crush on few girls in my college who are my juniors and 18-20 yr olds but this 23-24 yr old girl is the prettiest of all my crushes.