should i stop>>>

I recently became friends with one of my sisters friends and now shes been getting pissy at me. my sis is 20 and her friend is 21/22
friend=m
me and m play the same game and so thats basically how we started talking but my sister doesn't play that game at all even when m would ask, but she stays on her ps4 all day basically
I would play for a few hours after work with m and she would randomly call me sometimes to ask if i wanted to get on and m is a talkative person so she treated similar to my sis and just talks about everything

but now i feel like our friendship is making her shitty, a few things she said that kinda threw me off were, oh she can be ur friend, or i dont talk to her because she talks to u, meanwhile ik my sister only calls this friend when she needs to vent and m is rlly nice so i dont wanna just cut her off for no reason but i also dont want my sis to be shitty lmaoo
not to mention shes rlly my sisters only friend but she never texts m

//both my sis and m like men tho so its not a romance thing