Why is my girlfriend doing this?

My girlfriend and I have been together for 2 years and we have been very happy together thus far. We go on walks together, go out to eat, have great communication, and have practically been inseparable for the past 2 years. I Find her very attractive and I tell her that I love her multiple times a day. She was home schooled and has not had many opportunities to gain friends so she has been attached to me. I have always encouraged her to find friends and now she finally did. She met this guy from work to hang out with about 2 weeks ago, he is 25 while she just turned 21. At first I was thrilled, but now I am not so sure. Opposite sex friends do not bother me what so ever but it is whats been going on that disturbs me. I am not worried about her cheating at all we both trust each other. I met the guy and he seems like a nice fella, he is a little metrosexual but he is clearly straight. They hung out 6 days in row going out to bars and strip clubs every night while I am at home because I am not of age. He buys her all of the drinks and has spent over $150 in the past 2 week on her. He has stayed the night at our place a few times sleeping on the futon. I am never home for this because I work graveyard and he is usually over after I leave. They make popcorn, watch movies, and drink alcohol together like normal friends do but it's just the fact that it has only been 2 weeks. Yesterday i woke up at 3:30 when she got home from work so we could spend some time together, but she was tired from being up late with her friend, so she decided to take a nap. She slept all day until I left for work then woke up. I came home and the futon was laid out, popcorn was made and they watched a movie together. She has to work at 5:30 in the morning on top of all that. This really troubles me, not because I am jealous or worried but because this seems very insensitive and inconsiderate to me. I have also came home with them passed out on the futon sleeping face to face after falling asleep to a movie. I understood falling asleep but how many friends do you fall asleep next to face to face especially ones you just meet. It makes me wonder if they sleep together on the futon while I am not there? I also understand that she is excited to have a new friend to talk to and hang out with and honestly so am I, but this friendship is coming off very strange and is starting to upset me. I have talked to her already but nothing has changed. Should I just let this play out? Am I being too controlling, or is she just being really inconsiderate. what do you think and what should I do?