If she’s gonna be taking a buggy, perhaps a few bags, picking up a bag of shopping or two on the way home and occasionally having a friend or you in the passenger seat I would forget the teeny tiny cars.
The baby seats mean you need quite a lot of space to the front seat and it’ll inevitably go on the passenger side.
The buggies etc. take up a lot of space in the boot.
We had a little girl last October and had 2 Seat Ibizas; current generation and previous generation.
The boot takes the buggy and a couple of well positioned bags but not much else.
The baby seat position means you have to put the passenger seat quite a way forward. If I drive, my Wife doesn’t have much leg room in the passenger seat.
We decided after 4 weeks to get rid of my older Ibiza and get a C3 Picasso for my Wife’s daily car. I use her newer Ibiza to get about in.
I reckon the smallest you could practically get away with without getting annoyed/frustrated would be Ibiza/Fiesta/Polo/Jazz/Yaris size…