Argh

Okay I'm writing this really subtly as due to the openness and anonymity you've probably guessed none of my friends know about this.
I'm sitting here with C and the slightly slutty friend (slightly?) and she's fucking doing it again.
C came town with me today and we went and got McDonald's after and (yeah I'm fatty) then he came round mine to eat said mcdonalds...then my friend invited herself round. We were talking yesterday and I was like "well I kinda like him but it would never happen and shit"...apparently she took this as her sign to step in. He was round and I tweeted "eating chicken nuggets with purple hair"...5 minutes later she's at my door. Happy being the third wheel she always is.
She then starts doing it again. Being clingy and slutty just to try and get some attention.
I feel mean because she has been there for me through a lot but honestly it's a bit much. When he's cuddling up to me or we're play fighting and shell just suddenly be involved and we're both like "what?"...then he actually starts being closer to her. She's fucking got her way again. Which has annoyed me.
But then when she left the room I was like "you alright?"
And he gave this kind of eyebrow signal look towards her looking really irritated.. Then just said yeah.
So I don't really know what's going on all I know is she is irritating me right now because she can't stand someone else getting any effing attention.