Dealing with someone who repeats the same conversations over and over

My friend's GF is like that minus perversions. Unfortunately I can't set her straight since I'm not allowed to make her upset because then my friend gets upset with me.

But her GF is really driving me nuts, she is always on overdrive, can't sit still and talks faster than possible and basically never stops. When she is upset she does the same over and over and over, once I answered she says the same stuff asks the same stuff like I haven't already answered and if I don't say anything she says "Right??? Right???? Right?????" until I answer.

The worst thing is that my friend whom I hang out with a lot more, takes after her because the GF has said she is normal and we are not, so my friend copies her (being "normal"). She called me and babbled and repeated and I got angry and told her to SHUT UP. She was very upset, but I couldn't have one more person like that...

Her GF is so bossy I really wouldn't dare saying anything even if I didn't risk messing with their relationship because she is also utterly selfish. She always has a story to tell about herself, she teases other in a "funny" (mean, exposing their weaknesses) way and she is shallow. Other people seem to be there only to listen.

Fine I can listen if she talks normally, but when the repeating starts and I'm expected to just throw fuel on fire, I rather like to withdraw from the situation.