GIRLS: Is it strange to chat with a girl on Facebook?

Ok, so i used to be in engineering with this girl and we talked occasionally and now that I switched my major I havent really seen her much. This sounds really cheesy but...We were at a chemistry review one night and she laid her head on my shoulder and said "mm you smell really good." so, this was prob a year ago, but she just broke up with her boyfriend and I always thought she was really pretty but I didnt really try to do much bc of her boyfriend but now shes single...I dont have her number but we are Facebook friends...so girls, should I try and chat on facebook with her now thats she single, or what? (shes been single for a day...i was going to wait a few more days to let "things" settle).