I would do enriching activities with her just like any good parent would, but they should be at her level, not the level of a typical 3 year old. I don't think you need to do workbooks or anything of the like, but continue to talk about numbers, math in the real world, etc. If she is interested in reading on her own, allow her to do that.
It is going to be a challenge when she is finally old enough for kindergarten. My DD also missed the cutoff (but in her case it was by about 1.5 months, not 1 day). The district has an acceleration policy, which is mandated by the state, so we ended up doing a grade acceleration after she started kindergarten. If your district does not have a policy or they never accelerate, then that's not going to work. I'd probably start looking at private schools.
