Should I confront these two girls?

I apologise in advance for the length. I am in my final year of university and there are two girls who I would consider two of my closest friends there. We are all 21. Me and one of the girls were actually very close friends for the first two years, and then we later met the second girl. I was really happy to have met the second girl because I thought she was such a genuine, friendly and honest person; I really did not know many people like that. The three of us were great friends, and had several classes together. However, these days it is the two girls who are best friends, and it is not that that bothers me, but it is the case that they are leaving me out, and I have no idea why. I dunno if ¨threes a crowd¨, but for example, we all have a class together in the afternoon. I live at home and commute, and have to be quite quick in leaving in order to catch my train. These two are always the last girls out of the classroom, and then they hover around the door for 10 minutes before actually saying bye. I walk with one of the other girls, and I have waited for her 99 percent of the time, which has sometimes resulted in my missing my train. On the occasions I did not wait, I always let them know and gave an apology. So I felt like it was quite rude when the two girls, on more than one occasion, have rushed out of the classroom together without even saying goodbye or bothering to wait. I have tried to invite them to lunch and such, along with our other friends, and then one girl will say she is busy, but then I will see her with the other girl. I asked them if they were going to be at an event the following day, but they said they ¨did not know about it¨, which we had to reserve places for in advnance. The next day, I went to the event, and there they were, together. The first girl was organising a charity event, and I offered to help her if she needed it. She said thanks for that, and I was going to text her a couple of days later to find out any details. I then received a text from the second girl saying that they were currently setting up the event together, and asking me to go and ¨make a donation.¨ I used to think the second girl was one of the nicest people I had ever met, but now I feel like she does not want me there. She will engage in some polite conversation with me, but that is all. When I am alone with the first girl, we still get on well. It is true I was closer to her than the second girl, but I would never try to exclude the second girl, I always included her. I am always seeing them together and they have never bothered to invite me, even though I try to arrange stuff. Thankfully there are only a few weeks of university left. Should I confront them? Or should I just ignore them? Thanks in advance.

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