Need advice

I have a best friend who I love. we met at work and instantly clicked. we have a mutual co worker who I guess became our "friend"😆 that girl has a friend crush on my bff and literally said it to us and would feel a type of way if we didn't talk to her and she was wanting what me and my bff have when she just started working with us which was weird and me and bff always knew that and we would mutually agree she was weird but hey we won't obviously say that to her face and treat her any different to make her feel bad because we aren't rude and we felt bad so we tried hanging with her more and stuff.

fast forward to now, my bff has started growing closer with her which is fine, but she started to treat me differently. now she thinks I'm not being genuine with that girl because I'm acting the same way we always thought of her from the beginning which i think is unfair. Just because she chose to be close with her doesn't mean I should make myself uncomfortable and make my bff feel less guilty and stressed knowing I'm not too trusting of her like she is.

mind you that girl would literally make comments about my skin color and literally sent me a post recently with the n word in it and my bff knows all this and knows it's wrong, but blames it on me for laughing it off and that's the reason why the girl thinks it's okay to do that to me.

I don't think a grown adult would ever think that's okay even if someone tells them it's wrong in a nice way. I just tell her to stop in a nice-ish way because it's awkward she feels comfortable saying that to me and I'm like thinking well she is problematic and knows it's wrong.

And , my bff said I treat her differently when I'm out with the two of them and I act overaly nice with the girl when I literally am trying to hide the fact that I'm starting to realize you guys are surprising me with treating me this way and I'm not gunna lash out right then and there. I just observe and think "okay this is how it is? wow" and she thinks me doing that makes her feel that I don't treat her overly nice in that way when we are around others too, but she knows I only do that when I'm uncomfortable and trying to not have them know how I feel because they don't deserve that, I'm not comfortable, and I'm not ready to tell them right then and there.

I agree and apologized to her on how I'm sorry it makes her feel that way and I'll stop doing that, but that's how I act all my life. I feel sad and it makes me feel like she's telling me to change who I am over that girl when I've always been like that and it makes me second guess my character which isn't fun.

The fact that this is all happening and causing us tension is because of that girl is crazy. Our years of friendship too. I guess I need advice to know if Im doing something wrong like she says and how do I go about it? should I confront the girl or just keep telling my bff about how it bothers me how she needs to stop telling me to act a certain way because she decided to be close with that girl that literally did things to me and it's true I do brush it off to not cause drama and keep a distance I have with her. The girl thinks I'm close with her too and I guess it deceives her when she doesn't know what she does bothers me, but at the same time I know she knows like who would comment on someone's skin color and think that person is gunna be okay? and I don't even talk to her as much. she only texts me when she wants to know if I'm working on the days she's off so she can stop by and she doesn't have a comfort with me because she previously would express how she was wanting my bffs friendship so bad and kept asking if my bff hates her or annoyed by her which is why she confused that as us being close. sorry for the long rant.