I think my relationship has went completely sour

So i met this amazing woman in an online game. We hit it off and we played for hours every day while talking on discord through voice chat. We flirted while playing and it was absolutely amazing. I did feel we overdid it though since we did this for two weeks and could talk for 5+ hours and tried to step away a few days, but she requested my presence so it didn't work like that. Fast forward a month we both kind of wondered where this was going and admitted to liking each other. Well, it's long distance so we agreed to be exclusive, but also agreed to not become anything officially until we get to meet (damnable Corona).

After this though she changed. She changed terribly. She became withdrawn and hard to speak to. My flirtations were unappreciated and she was uncertain about the future. She stopped being nice and was talked to me in a cold robotic kind of way. I brought this up but she became upset and telling me nothing is wrong. She stopped asking to hang out with me, but still initialized text if i withdrew to see what's what. She always at the end of the day say just something like "Hope you had a good day" and that's it. She'll respond a few messages if i tell her about my day, but then it goes dead.

Now, if i suggest a day to hang out she always has excuses. They range from headache to actually having promised some other guy friend to do something. She never suggests to do anything with me anymore and it's been about a month of this crap already. I know she keeps playing with someone else and i haven't been acting insecure really and just let it be. But everytime i ask her about hanging out, i get an excuse, and the rare time we do hang out, she doesn't sound like she's having fun at all.

Yet she keeps playing with that dude while telling me that we're fine and that i should stop worrying if i ask her what's up with us lately. I did ask her if i could join them (i mean why not, it's her friend right) but then she just ignored the message and left it at that.

My thinking is that she told this friend about us and suddenly he confessed his feelings or something and now she's confused, while obviously leaning more towards him. Sounds like a typical story when dating a girl with a long term single male friend, but that's just speculation.

My question is this. What would be the best way to go forward? Just stop communicating to see if she gets the message or just tell her that this is not working out? I'd hate to drop her cold based on what can be me overthinking it and be completely wrong.