Breaking up with my girlfriend soon, how do I do this?

I (18F) have been with my girlfriend (19F) since the very end of March. We’ve met in mid February and since we met on a dating app met up IRL for the first time around mid April. Since the meet up I feel as though there’s been a dramatic shift in our relationship. I am unsure if she feels the same way but it’s like we’re only dating by title now, and we’re actually just acquaintances. She never contacts first, all sort of affection has been gone, her responses to my messages feel very one note and as a result it’s hard to carry a conversation with her. I have the tendency to gaslight myself so I have sent some screenshots as confirmation on if that’s what’s been going on or just my imagination to my friends and they seemed to agree with me for what it’s worth.

I don’t feel too hurt by it now, I was when I first noticed the pulling away and attempted to cling on more but gave up on that. No real feelings for her exist now, mostly just anxious about calling her to break up (shortly after we met IRL and she was done with her college year she went to go visit family where she still currently is, too far for doing it in person to be possible)

I have discussed to her before how I want to spend more time with her, and she has said herself she knows that we haven’t been talking as much and blamed it on her depression acting up. Honestly I’d be perfectly fine with this and try to support her. I have my own mental health issues and have isolated myself when they’ve gotten bad. My issue is that we have some mutual friends who we’re in a group chat with together. With these mutual friends they regularly hang out virtually most night for 4-6 hours. Often playing game titles I do not have and due to personal reasons cannot buy at the current time. As well as looking through their messages in this chat she does not seem nearly as distant as she does when it’s just us. I am not suggesting I don’t believe she’s actually struggling with her mental health. But I don’t think I’m asking for much out of a relationship for her to engage in an actual conversation if she has the mental energy for that. She’s also blamed it on not having anything interesting to talk about; and while I don’t think I have much of interest going on she gives those very one note responses when I attempt to get something going.

I’m not sure what happened, the date went well and when we talked it over we seemed to be on the same page. Guess these things just happen sometimes. I know the right call is the end this and not keep it dragging one because it seems like she for one reason or another decided she doesn’t want to keep this up but doesn’t have interest in telling me that. I just don’t know how to have this conversation without it seeming so accusatory or like I’m trying to put the blame of everything on her. This is my first relationship so I’ve never broken up with someone before. I want to write something out to go off of for when we have this chat, but I genuinely don’t know how to even start this conversation appropriately. I want to make sure I do this correctly, which is why I’m making this post.