Asami did outright say that Touko was bragging about her boyfriend again, so this is, at best, cheating or, at worst... well, you know.
You read wrong, she's talking about another friend.
With this author, next chapter we learn that Touko is sleeping with a bunch of other girls. The fact that she knows the > nurse won't be back make me think she's accustomed to it.
Oh shoot, she's talking about a "Ayumin," not Touko. Whoops, disregard what I said then! I have more hope that this will end in a yuri fashion then.
Edit: I certainly wouldn't be surprised by that development... it's basically the same thing as Nadeshiko Hiyori except only one girl is sleeping with a bunch of other girls and not both of them... which is really not the same thing at all now that I think about it.
Nadeshiko was more a story about Polymary, so it will be interesting to see what direction this one takes.