I need urgent/serious advice about my friend pls.....?

I have this friend i have known since middle of 07. she is a pretty nice girl and she was the first person i met when i moved to a new city, she took me out and she was always there when i needed her.

However there was a time I needed a place to stay and she let me stay at her place, and I said i'd pay her some of the rent, she was going away so she gave me full rent for the place and said not to worry. But i think she told another close friend of hers that I stayed there and hadnt paid her the money.

Anyway the latest thing that happened was she had a fight with her close friend and then this close friend of hers(who is also my mutual friend) started calling me more, and telling me stuffs about my friend and also told me about the house rent issue of 2007 that she said i didnt pay her, and also said a few other things. This made me upset and i lashed out at my friend and we texted back and forth and insulted each other in a very bad way.

she said why was i even choosing the other girl over her, that if i knew what kind of girl she is, i wouldnt be talking to her.

anyway i miss my friend so much now and if i had something really deep to talk to someone, i think about her, but i fear we may have lost our friendship with letting others get in and with little bickerings on the side. Do you think I can do anything to this?

is it me who needs to apologise or her?

Im still talking to the other girl but she's not as close or someone i cld trust like my friend.

what do i do pls and how to remedy this?