if the company is big enough, i would strongly suggest going to speak with HR for some advice on the best way to deal with this girl. Alternatively, ask your boss if there is someone else that can be your go to person...possibly with a desk allocation next to them for the next few weeks while you finish getting up to speed.
It is possible this other woman is going through something out of work that no one knows about that could result in her jeckle and hyde type personality...ivf or other treatments can play havoc with moods. Not excusing her at all...but, it may one day be explainable. It is hard not to let this sort of stuff get to you but try the keeping a tally idea to have a giggle or think up some good come backs (ideally funny to lighten the mood). Make an effort with other team members, even if just getting a coffee once a week or so.
I hope things improve, it is amazing how much 1 person can effect us.