My 2yo has made up a fake woman

Not really, but after we picked my partner up from work she said "I want new mummy, not old mummy" when she was having a bit of a welly, and kept saying about "new mummy." Now, we both sort of laughed it off after the fact but I can tell that it has upset my partner a bit. She kept asking small probing questions like "where did you go with Daddy today?" (to which our daughter answered with the stuff we actually did, like go to the shops to get pet food, played with blocks, read books etc.)

Now, I'm not having an affair and nor do I ever intend to, but even if I was I damn well wouldn't bring my child along, and there is absolutely no chance I'd say "this is your new mummy" or anything like that. I feel like the more I try and defend myself the more my partner thinks it's real. How the Hell do I dig myself out of this non-existent hole?

I can imagine that it doesn't help that I was dressed quite nicely today with aftershave on, but it was just the first outfit I grabbed this morning and our daughter likes to smell perfumes and stuff.

I get it from her perspective, because something like that the other way around would probably have me thinking "what the fuck?" too, but kids just say shit sometimes.

Edit: Thanks for the replies everyone. Having read through them all, she has probably got this from me just chatting to other parents at playgroup. Despite the comments about ghosts and past lives, I don't think there is anything paranormal going on here lol. Anyway, I'm going to count myself lucky given some of the stories you guys are giving about the stuff kids make up!