If she's happy & alert and giving you those wet & soiled nappies.. I wouldn't worry too much.

If she's pushing the cereal straight back out, she may not be ready for solids just yet. There's some great threads on the boards here about baby-led solids, and how to know when bub is ready for solids, which you could get some info from. If you're concerned about weight, I'd up the milk feeds, as the food we usually start them on (fruits & veg) don't have many calories anyway.. so not really conducive to gaining weight