Poop does change with solids. It isn't digested as quickly as breastmilk, so she won't go near as often as she used to. Some babies still go a couple times a day, some less, it really varies. The consistency changes too, it becomes a little more solid and sludge-like. You'll know if she's constipated if it seems like she's in pain or uncomfortable (it's hard to distinguish this from gas or tummy ache), if you see her straining to go and nothing comes out, or if her poop is rock hard and looks like little marbles or pellets.
For the gas, you might try Mylicon (not sure what it's called outside the US). A dose before bedtime might help.