Be careful with going to a mostly, or all, fresh food diet. Pellets and seeds are meant to be a staple part of our birds diet. It can be
very difficult to provide all the nutrients are fids need by only (or mostly) feeding fresh foods.
I think it is better to feed your fid seed as the main part of her diet and supplement with fresh foods then for her to be on an all seed diet or mostly fresh food diet. Seeds get a bad rap...they really *aren't* that bad when the bird is eating fresh foods as well.
I would limit to giving her fresh foods to twice a day. In the morning and at dinner time is a good choice. Remember to never leave fresh foods in the cage for more than a few hours (I usually only leave it in for an hour then toss it into the trash) as bacteria starts to grow quite quickly.
As a side note, there isn't much nutritional value to lettuce, so I would try other leafy greans like kale