tenant has given a doctors letter

Tenancy Types and Management

never seen this before, but a tenant has given our agent a doctors letter to state they wish to move out immediately. this is a joint tenancy and she is in employment, but cannot seem to cope with living with the other occupiers/sharers. the agent hasn't got any other information from her. she is also in arrears for 2 months for her share of the rent. would you have her settle her current debt and let her go? if so, this sets a precedent for other tenants to think they can walk away from obligations with a doctor's note! frustratingly the agent didn't think to take a guarantor for someone in full employment - if she can work, can't she move out and pay the remainder of her debt until she finds a replacement tenant?