Anxious and uncomfortable situation/friendship

Hello everyone. I'm in a situation where I don't know how to react. Only I met a guy who I fell in love with. Currently he doesn't want a relationship because of his past. So we're friends for now. That works out decently. I got to know his best friend who became my "best friend" too. I learned that she had feelings for him twice but it didn't go any further because of him not wanting a relationship at all. A few weeks ago after her (his best friend) boyfriend left her she talked to to man I fell for ( let's call him K.) about how she was in love with him twice. But she (let's call her P.) said she's not having active romantic feelings for him... I think that's not true because of the things P writes on a social media platform where we all met. It's pretty obvious that she loves him. Thats the background. Now I can see that she tries to provocate me with her words, our connection got worse, she made accuses which aren't true. She said I would sometimes flip a switch and change my behavior. Which is not true. That I would question their friendship which is triggering to her because of her past. But I didn't. Their friendship is quite obvious. Between K and me everything is fine. He knows about my feelings and he's helping me to feel better. But the problem is that I'm afraid she could talk negatively about me in front of him and that he would believe her. That her false opinions would weigh more than the truth. That she'll ruin the friendship and everything what could might be as it seems that he isn't totally uninterested in going further with me than a friendship. He seems to be just very carefully and moving forward VERY slowly. Which is absolutely fine. I feel uncomfortable to talk with her because I don't know how she interprets my words, maybe in a wrong way. So I'm afraid to talk to her. I'm afraid to talk to him about this problem because of the possibility that he would believe her more than me who's speaking the truth. I can even show screenshots of the conversations with her. Its driving me crazy that in private messages she could say untruthful things about me. Im scared to lose him since I fell really deeply for him and finally he seems to come closer in tiny babysteps. I don't know what to do with the situation and I hope maybe someone could show me a direction where to go :( Thank you for reading my text.

Thank you for your answer! No one of us is hanging. I think I didn't explain it good enough. He said no to a relationship. With her he's just a best friend. With me like a close friend but there are small hints that he could feel more for me in the way he acts and talks sometimes but he didn't want to admit them at the moment. Which is fine. He doesn't give her the thought she could have a chance and with me openly its the same except for the little hints.

Let me take a shot at this. It appears that you and your friend (P) both like, or potentially like the same person (K), correct? It also appears that the conflict you have with your friend (P) is coming from this mutual infatuation. So my question for you is this. What relationship do you value more? You may not be able to keep them both. It is always best to be honest and candid with both of them. Treat both of them like you would want them to treat you and be prepared to accept the consequences. Let us know how that goes.

I simply would have a conversation with "K" and have a conversation with him about your concern. I would say something like...I'm worried that "P" is going to sabatoge any feelings you could develop for me and I say that because to "me" it is very clear she is attracted to you...I want to ask you that if she says anything that is derogatory to me if you would be open to sharing what she says about me so I have a fair shot at addressing any upcoming issues. I would say I am uncomfortable now with my friendship with "K" because I feel she may take things I say and twist them in ways of which to turn you against me.... Not a long dragged out conversation (because guys don't like drama) but that it is JUST a concern you want to quickly mention to him because it is weighing on your mind. And as far as the friendship between you and "K" I would step back as much as I could from communicating with HER...OR I would have a conversation with HER that goes something like this: I understand we both have feelings for "K"...it makes this friendship hard...and I think we should keep (if we stay friends) our daily chats limited to US vs. you and "K" or me and "K". We can't control what others say about us...You and your actions will show this guy who you are and what you are about.... See if you can stop worrying about "her" and just focus on "you"...and whatever your journey will be with this guy.