Completely agreee I've done the same with my 3 they each have a tablet and it keeps them occupied especially on a long journey too.Not defending her but I do that. Even got my little one a tablet for Christmas. I rarely get breakfast so I need something to keep them occupied whilst I get stuff done.
I hate to say this but when my eldest daughter was growing up she learnt so much from watching the TV - ok she wasn't quite Wilby's age but even from the age of 1 she loved the TV so it can do some kids good. When she was 3 there was a programme teaching you how to draw and she picked up so much from it.
Even the schools encourage you to use a tablet at home to do work on Maths Apps.