Competitive other GP

I haven't really shared this as after what happened with my last GC (totally estranged forever, will never see or hear from them ever) which is making me feel very, umm, insecure already and this isn't helping.
A different AC's partner is about to give birth next month. That's beautiful, brilliant, fantastic BUT her Mother is sooooo competitive its making me seriously want to tell her to drop dead, which I wouldn't obviously but I feel so p'd off. She has already made the statement that she is going to be, and I quote, "favourite Nanny". Everything I do or say she contradicts or googles or texts someone to check details and comes back to me with "actually blah blah blah". I walked the AC dog yesterday as they are away for couple of days and left a note saying how good he was and how happy he as to see me - went back this morning after the other future GP had been in last night to find a note saying "Shep is ALWAYS happy to see me and is always so excited when he just hears my voice".

Its driving me bonkers and I don't even see her often. I'm dreading what is going to happen when the baby is actually here. I don't want to be in competition with anyone, I just want to be able to enjoy my Grandchild.