Replying to Crazy good looking girl sits next to me every day I have girlfriend though lol its so hard doe

I have this girlfriend and she is cool, we are friends who sleep together on occasion and she looks very good but she acts young and is young I thought I was done with girls like that. I honestly wouldn't care if she left and saw some other guy but I still like her if thats understandable.

So now there is this other girl that is extremely gorgeous 9.5/10 and she is always sitting next to me in class. I never really acted too interested since I have a girlfriend, but I have been nice to her all year helping her on tests giving her answers.

Now we started talking quite a lot more and we are meeting up in the library at some point. Im just worried what the "girlfriend" or what ever will really think?

Its so hard I go to parties with my girlfriend all the time and all these girls I know kiss me and hug me and I try and ignore it and go to my girlfriend, but I cant ignore this girl in my class at all. too good looking.

What should I do????????????? This girl is insanely good looking and she is nice so far but she is going to be much harder to impress, but lots of girls like me.

Help me before I may fuck up