Notice period

Possession - Section 8 and Section 21

I have a dss tenant who's 6 months tenancy is up on 31st March so on 11th February I issued her notice to terminate tenancy as from 1st April.
The council have told her I have to give 2 months notice so I said I'm happy for that to be 11th April, they however say I must reissue notice for 2 months from now? Is this the case?
She is struggling to pay rent and pays it in dribs and drabs less and less each month and if she stays another 2 month she won't be able to pay rent and that will affect me paying my mortgage.
Thanks in advance.