I manage a large team of all women bar 1 man and if this was happening in my team I would want the person (aka victim) to tell me about it quick smart. It sounds like she is vile and you don't know the back story. They may be trying to fire her for her vile behaviour and have her on final warning and are just waiting for that last piece of evidence. The others probably aren't friends with her, they are probably just being pleasant with her to keep her vileness away from them.
It costs a lot of money to hire and train staff so if a new starter is happy and performing well, but is considering leaving because of the actions of one team member, there is a very strong financial motivation for your employer to do something about it.
Do trust your manager to handle it in a discrete and sensitive way. Be open with them about what you are feeling and tell them everything, even the stuff that may seem insignificant or petty like the coffee shop thing.
I am sure your manager will help you work it out!