Is my 21F gf losing interest in me? I'm 22M

We are in a 2 year relationship. We instantly touched, quickly fell in love, and got intimate within the first month. We used to have sex almost everyday. And no, I didn't force her or manipulate her. She liked that. Everything is consensual.

5-6 months ago, we dropped the frequency. 2 times a week. I am comfortable with that. I have a huge sexual appetite but I never forced it on her, whenever she said no I respected it. I have never cheated.

But since the past 1-2 months the frequency has changed we have sex once a week, and in that I feel like I'm forcing her to. There's no initiation from her side. When I initiate, she pushes me away in a sort of rude way, and says 'no' in a bit rude manner and gives some reason and avoids it.

One day she pushed me away in such a way, and I was sort of disturbed by it. And she could read that on my face, we got drunk that night and she asked me "You're mad cause we didn't have sex, right?" I was honest and told her "yes, I was really in the mood and it has been a week we haven't had sex" (Now I know once a week too isn't a bad frequency, but please feel me, a girl who drooled for me has suddenly no more interest in getting intimate with me) and she says "But when I say no you should get it, the matter ends there." And I got a bit sad after that. But just for the sake of it, she initiated, no passion, no foreplay, she started and felt like she wanted to end it quickly. After 4-5 days the same thing occurred she pushed me away and gave some reason.

Last time I tried to initiate was on my birthday night, and on each other's birthdays we had sex. We know we make our birthdays special and have a great time. But on this birthday, I initiated and she said it's too hot and again pushed me away rudely. I was upset again, not in the way I shut her down or got rude to her. I only stopped babying her, but I still asked whether she had lunch the next day whether she slept well. I just acted like I lost interest, that too for her to at least explain to me what's going on. I'm clueless. But she got angry because I reduced interest and didn't babied her. And in a month, we are going long distance. So at least this is the time I expect for a lot of sex.

I am totally ready to give her, her space. I am ready to respect her decision. I'm mad, because I don't know what is causing this? I'm fit, I'm disciplined, I'm focused on my career I haven't changed since I met her. I even quit smoking for her.

But, besides the sex part she is normal. We laugh, we give presents to each other, we go on rides and stuff.

And I'm hundred percent sure, she is not cheating on me, she basically hangs out with me all day. She doesn't hide her phone. All her girl friends are in a healthy loyal relationship.

I just want a healthy, fulfilling sex life. I don't want to end up living a life where I have to beg every time for sex and I certainly don't want to cheat. Is she going through any hormonal change? Or does the summer really mess up women's mood? How can I effectively communicate?

She is currently mad at me for not babying her because she pushed me away, and I'm too upset that at least on my birthday I could expect a romantic evening.

Every advice besides breakup is welcomed.