Why did she suddenly stop talking?

Had a thing with this girl I met recently at a party, we ended up having sex that night and again in the morning and its been the same for the past 2 days as well, hanging out at hers, talking and laughing, having a good time and having a lot of sex. Even after sex we would cuddle and kiss so it didn t feel like just sex. We have very similar interests and we were getting on so well and I really enjoyed her company and it really seemed like she enjoyed mine too but she has suddenly just stopped replying to me and isn t making an effort to talk to me either, when we were texting all day before this. I m very certain I didn t say or do anything to upset her and I was just wondering if there was any other reason she would suddenly stop ?