My Girlfriend Thinks I Don’t Longer Like Her

So me (M23) and my GF (F22) have been together for 1,5 years now. We met at work and after some time dating we decided to give it a go and be exclusive to eachother. Things have been great overall, we see eachother approximately 3-4 times each week and we talk to eachother daily. Now I just started a new job and haven’t had as much time as I had before. Today we had a party for which she had to reschedule a shift because she works in the weekends also. After this party we split up and I went to a friend of mine that I hadn’t seen in a couple of weeks. I could see that she was visibly upset that I did not stay with her. Because of this, I decided to call it quits with my friend and I went to visit my GF about 30 minutes later. I could see that she had cried, which obviously affected me. I asked her what was wrong and she started talking about how things have changed and started telling me that if I no longer like her I should break up with her etc. I told her I did not want to split up, as I still like her as much as when we first started dating and I can’t imagine me not being with her. However, due to some confidence issues from her side I can not seem to let her believe this. I don’t want to gaslight her by telling her she is imagining things and making up scenarios, but I am very hurt that she would think I will end the relationship with her and I can’t get over the fact that she even brought it up. What do I do?

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TLDR: My girlfriend thinks I want to breakup, but I don’t