Fear not! As no further fixed term lease was signed, her tenancy automatically became a Part 4 tenancy which includes any special conditions in the original fixed term lease (e.g. No smoking in the property). Her current Part 4 tenancy is a continuation of her fixed term lease but with less security of tenure.
However, if she intends to vacate and move somewhere else, the Part 4 tenancy is more suitable as she only has to give the correct notice in writing providing the correct notice period which, as she would have been in the apartment for more than 1 year but less than 2 years, would be 42 days.
If she talks to the agents, they may agree to a shorter period especially if she allows viewings before she leaves. These viewings should be allowed on certain days at certain times - say Wednesdays afternoons between 2 p.m. and 4 p.m. and Fridays in the mornings from 1 a.m. to12 midday.
If she had a fixed term lease, she would have to get permission for an assignment and find a replacement tenant and pay any expenses involved. Under a Part 4 tenancy, she does not have to find a replacement tenant.