This is an interesting one.
OP, was your friend working at the time of taking on the tenancy?
As PP have stated, some lenders do not allow buy-to-let landlords to rent to people on benefits therefore rendering their insurance void. Effectively this means that the borrower is in breach of their mortgage contract.
Therefore, should she sit it out and wait for the court to seek possession she is placing herself in a predicament.
In terms of the Housing Act, her landlord is required to serve the correct notice, which is a S21 and/or if she is in any rent arrears, a S8. (There are many grounds on a s8)
What I'm intrigued about here is the position of her local authority and how they are going to handle this one. She does need to explain the reasons her landlord has stated.
Many LAs advise the tenant to sit it out, in this case, that would be poor advice as if her circumstances have changed and she is now in receipt of benefits, and the owners lender stipulates that he/she is not allowed to let to people whom aren't working, there is a no-fault on either side.
How long notice has she been given? How was this served, is she able to speak with the LL?