TLDR at the bottom.

I have been together with my girlfriend for almost 7 years. Last month I've realized that after I'm married there's no way I can get back to flirting with girls. And my girlfriend is a drama queen. I tired of her shit.

Recently I got into new college. I met this girl from class. Younger than me. I'm catching her positive vibe. Very fun when having her around. I make a move a few weeks back. Giving her attention. Compliment her something like that. And that she responded kinda good. Like she wanna talk to me when we have time. She laughed at my joke. Plus, I used the ignore method. I ignore her for a day. Like she didn't even exist. At first, she's trying to get my attention. After a few days, the ignore method do not work anymore.

We usually talk about college stuff. Nothing too personal. Planning to text her tonight. Bear in mind, this girl and my girlfriend knows each other because​ we all in the same class. And she knows I have a girlfriend.

Should I text her? What's my next move? What should I do?

TLDR; LTR with a girl for 7 years. Want to make a classmate to be my side chick even though she knows that I have a girlfriend. What should I do?

Sorry for bad English.

Really appreciate this community response to my question!