Thanks for your reply.
I'm afriad she will be bound by the full term of the tenancy agreement unless there is a break clause in it entitling her terminate during the term or the property is unfit for human habitation (which would also entitle her to terminate provided she could prove the same).
However, landlords are under a duty not to unreasonably refuse a suitable tenant and her focus now should be on finding one. If the landlord acted through agents then she should explain her situation to them and press them (and continue to press them) to find she finds a replacement tenant. You can then use http://www.gumtree.co.uk/ to find a tenant (private landlords frequently use this service.
The alternative is to offer the landlord a sum of money to in order to execute a surrender of her part of the tenancy. This would be where both parties confirm in writing that the tenancy has come to an end.
If she does not pay the rent then it will be for the landlord to sue her for the remaining rent. Landlord's usually obtain judgement on rents owed from the date the payments ceased until the point at which the landlord could have been reasonably expected to find a replacement tenant for that tenancy. That there are only a few months left does not help - there will not be a huge market for a 3 month tenancy.
If he sued he would probably get judgement on all or most of the money she would have paid until the end of the term.
Sorry it could not be better news.
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