A lot of the parents I work with ask us advice on this sort of stuff.
To facilitate language development, toys that encourage imaginative play are perfect (eg kitchens, shops, doctors sets and so on.)
If you are trying to encourage vocalization of any sort, then things that reinforce sound making are great, such as computer programmes where a child 'speaks' into a microphone and something happens on screen eg a penguin jumps into the water.
I would particularly recommend a company called 'Inclusive Technology' who make BRILLIANT stuff, in partic. excellent computer programmes for about £40 each. They are also such nice helpful people . Primarily aimed at people with s/n but suitable for all. Sorry, don't have number on me, but website should be easy to find.
Also in educational mode, ask your salt or SENCO if you can have a look at their catalogues. There are thousands of brilliant things out there, but due to the nature of public health and educational funding, you will only see a fraction of them. Absolutely nothing to stop you ordering from brill catalogues like the Winslow Press or Psychological Corporation. (Alsohave excellent text books on various things which are readable.)
I use a lot of salt stuff withown kids and extended family-they all love it!!
Of course, you may want to run screaming at the idea of 'educational stuff' in which case just go with whatever she likes (but Ipromise you, 99% of kids would like the stuff Imention.)
One more thing-sometimes I've known a family club together to buy something more expensive like a sound beam-sort of pole which gives out invisible beams-when someone moves in the line of the beam, sounds occur, higher/lower quieter/softer according to nature of the movement. Quite pricey but brilliant fun.
One MORE thing-some s/n equipment unnecessarily expensive (notInclusive Technology though!) For example I/ve seen people buy expensive bubble tubes, and fibre optic thingies for their kids (esp ones with Autism) but you can get them at a fraction of the price in Argos or novelty shops.