HB Tenant - possibly two tenancies?

I have a possession order which has expired and the tenant is not giving us possession of our house so we may have to resort to the bailiff route :(. We are in receipt of her Housing Benefit directly as she is in rent arrears. We believe she has found some where else to live and is in possession of this property which would mean that she may have signed another Tenancy Agreement (let via agency).

As of yet she has not requested the HB to be transferred to the new property and I think she is still living in our house.

However, surely she is potentially committing fraud by having two tenancies running and claiming HB on one? I am assuming she has signed a new TA based on the fact that she seems to have the keys to this new property and has been seen putting possessions in to it.

I did also wonder if the council contacted her regarding the other property and she wanted to retain her housing benefit claim, that they could 'force' her to confirm that she has ended her tenancy with us and has moved out. If the Council had this from her then could we legally reclaim possession of our house?

I have read that in law the person claiming must give proof of the Tenancy before HB is paid.

I guess the same applies to Council Tax - I think she is exempt for payment of Council tax on our house but surely you cannot rent two houses and qualify for council tax exemption?!

What do you think about this....