My advice is the lightest one you can find as you’ll end up carrying it at some point
This +1.
We went for an Islabike Rothan – 3.5kgs, well thought out, rear brake, low standover height, proper tyres, tough and great build quality.
Daughter #1 loved it for 2 years and when she was ready she transitioned to riding a Cnoc pedal bike in literally 20 minutes.
Daughter #2 is just starting on it.
They are pricey though, so definitely consider buying second hand. If you do then you’ll probably sell it on at much the same price if it doesn’t get too abused.
(Played with a Frog Tadpole and that was also a lovely little bike)