M.H.
My 2 1/2 yr old is 39 inches tall and 38 lbs, I know what you mean! (4 y/o brother is 57 lbs and 46 inches!) So I would suggest not spending too much since she will likely;y be out of it in a year. Anyway we had great luck with a side-by-side double jogger. The one we had was baby trend I think, but we bought it at a garage sale for $30. (one of the many strollers we purchased for our boys, definitely our favorite). Anyway it was easiest to maneuver with the heavier children, they had plenty of room, and it had 5 point restraint for the baby, convertible to 3 point for the big girl.
My little guy still fits comfortably in our Graco duo glide, and we did like that a lot too. it was nice to snap the baby carrier into and folded up really nicely. Our big guy grew out of it before he was 4, so its in great shape, and no use to us! That one was 250 with the carseat...likely less without it.
Hope this helps!