There is this girl that we hit it off from the start. We constantly tease each other, she had made a couple compliments about my appearance/style, we asks me to go together to the clubs to meet our co-students, we are touchy with each other and she invites me when she goes out with her friends. I find her attractive and I enjoy her company.
On the other hand it is not unusual for her to cancel our plans, all the times i asked her out she always brought a friend along so we were never alone. When a girl asked us if we were dating she said "dating with <myname>? don't be silly" and she made a similar remark when it was just the two of us. She once invited me to sleep at her house after a late night out, but her bestie was also staying (I went home instead, it wasn't even far). This goes on for a few months now, perhaps the signs are clear whether she likes me that way or not, but I can't tell at this point. If I was more assertive it would be clear by now, but I didn't felt comfortable making a move when we were out with others.
In some of the classes, there is another girl that made a few more clear hints that she is interested in me. She is a very nice person and I like her more that the 1st girl.
My main question is; can the thing with the 1st girl be considered, by any stretch of the term, dating? I personally don't think so but then again I am not that experienced in dating. Secondary question, should I go for the new girl, and if I do so, will it make things weird between the three of us and perhaps the rest of the group?
I am 28, both girls are in their early 20s for all that it matters.