I've been chatting with this girl (lets call her Amy) for 5 months or so as "the other guy", or the latest guy for her to have feelings for while also talking to this other guy (Bob). Amy had visited a friend of mine from a far away state. Amy and I met at a party and through discussion of future travel plans she had with Bob, she explained Bob was a friend and she had become annoyed with how bad he wanted to date her. Amy and I hooked up, and went on a great breakfast date before she left, and we continued to chat via facetime and text for a month or so before learning that I had been actually been promoted and was required to move to her state. After letting her know, she informed me Bob had sort of dug his way into the picture, but that Bob originally hadn't been when we met. I had been a "breath of fresh air" for her compared to Bob's constant try-hardiness, so she was really into me at the time and did not expect to like me so much or even have a chance with me.

I decided I wanted to keep talking to her. I told her I really liked her and enjoyed spending time with her, and it was none of my business of who else she talked to, so I didn't care. She seemed very happy about it. It went really well for the next 3 months or so. I ended up visiting her in her home state, and we had a very romantic couple of days together.

However, she recently went on that trip she had planned with Bob since the beginning and now things are completely different. We went from texting every day and FaceTiming every week, to only a few texts a day. She does not respond positively or playfully to my flirty texts. She admits she is awkward and is bad at flirting (pretty true), but she seems to send quicker, friendlier texts these days as opposed to fun, flirty convos.

I've stopped texting her altogether. It seems clear to me she is into the other guy and our conversations aren't fun anymore. However, I still like her a lot and feel like a have a genuine connection with her, and I feel like I don't want to throw this away or make things sour with us if something were to happen with the other guy. Is it at least worth letting her know how I feel? Or am I better off leaving it alone?

TL;DR: I've been competing for a girl with another guy and hes winning, should I walk away or let her know what I'm feeling?