Richy
I have a few houses that I let and it is definitely the landlords problem on one condition - that the break-in was reported to the police and they have noted the break-in.
If you did this then the landlord has no option but to pay for it herself or claim off her Landlords Insurance. I have mulit-tenancy insurance which covers all this and by rights she should have insurance too.
I would get in touch with her and explain this, if you get no success this way then send her a solicitors letter explaining the situation and demanding your deposit back.
Good Luck