Please help me..

Sorry it is so long...

But my boyfriend has this female friend from a totally different school who asked him to her Junior Prom because her boyfriend will not take her. My boyfriend asked me a few weeks ago and I said ok only because he said they have been friends for like 3 years and I trust him. Then, I was on his phone because he said I could be and in their messages she asked him if he wanted to get a little drunk before Prom and my boyfriend said he might not drink but he might smoke before.. I pointed it out to my boyfriend and he said he never likes to go to those things sober. I told him he better this time.

Then today, I started thinking about why she asked him and not another guy from her school or a girlfriend to go with. She must have other friends in her school to go with. So why ask him unless it was for some reason.. I don't think I can trust her...

What should I do? Am I overreacting and over thinking? This is so upsetting to me and I don't wanna be like this till May, so someone please tell me if I am just being over dramatic or what I should do.

*No hate please, I am so sad and worried.