I work in lettings and this situation is nothing new.
The landlord is being more than reasonable asking your daughter to find a replacement tenant and if I were her, I would be doing exactly that.
If the Landlord is happy with just that, then she should put a small ad in the local paper.
I think she is getting off very lightly as she is legally bound for 12 months....and finding a new tenant is the way out.
Why did she sign up for 12 months in the first instance? She must have requested it initially, or agreed to it as most tenancies are 6 months in the first instance to judge the type of tenant etc