Any software available for this?

Hi,

I'm looking for some software that will help my niece with her English homework. She gets mixed up on some words (they're, their, there, we're, were, where, to, too). She knows what most of them mean individually but gets a bit confused as to which ones to use when writing (especially on to and too).

She uses stylewriter sometimes, which has helped her grammar but I'd love to find some software she could use to help her understand the differences between these and which to use, anything I say goes in one ear and out the other.

I know it's probably a long shot but it's worth asking.

Thanks