Winter Bottoms
The bottoms do most of the work in winter. Fleece lined leggings for the really cold mornings, knitted pants and cords for the in between days, and tights that go under a dress without her complaining about them.
Newborn to 7 years, in colours that go with everything she already owns, which is the whole point. A pair that only matches one top is a pair that stays in the drawer.
Kids Winter Leggings and Pants: Your Questions Answered
The fleece lined pair has a brushed inside and is the warmer of the two, so it's the one for a cold morning. The knitted pants are softer and roomier, better for a day indoors or a milder day out.
Yes. The smaller sizes are cut with room through the seat, and the waist is soft elastic rather than anything that digs in.
If she's between sizes, go up. There's an elastic waist, so a slightly long pair still works and you get another season out of them.