If she's broken a £200 phone why not get a £30 replacement in case it happens again? Unless she uses it for more than calls and texts.
For the sake of saving £150 (£200 less £50 excess), I'd not bother with the home insurance. You'll pay for it come renewal time when asked whether you've claimed on it in the past x years.
Why don't you just get a pay as you go phone from three and switch out the sim card (assuming it still works) or have the number transfered due to it no longer working.
The C903 is £140 from the three store and there are cheaper options
Probably a C510 for £100.
UPDATE:
Hooray for contents insurance
They agreed to send me out a cheque for the current price of the C903 from Three less my £50 excess which works out to be a cheque for £70 (would have been £90 a week ago though)
Now I can have a look at getting a replacement from the pay as you go phones on Three's website
My question is now this:
Any of these phones stand out for £150 or less?