I'm sorry...I wouldn't wish this on anybody. It's hard to say. Does she have amnesia between alters? Maybe co-con? Anyways...

Just be a friend. Accept what happens and get to know each as they present. Usually a person gets assigned an alter until a trigger is encountered. Not everyone of them is going to like you, sorry to say, but that's to be expected. And if one presents that doesn't like you, I'd just say "I'm sorry that you feel that way", then I'd excuse myself. The other that knows you might return sooner or later.

It's always an adventure with this condition. Let us know how it goes.