My DS (now almost 3) was similar at that age - big vocabulary (300+ words at 18 months) but sloppy articulation. We noticed a dramatic, dramatic change when he moved 'up' from the 0-18 month room at daycare to the 19-30 month one; I think it was the change between the baby room where most of the kids only spoke a few words if at all, versus the toddler room where the 2.5 year olds were at least closer to his (1.5yo) verbal ability, so he could talk to the other kids.
So, if I were to suggest anything, I'd say give her lots of opportunities to talk to other children (at her verbal level, not necessarily her age level).
