Using your own home for this is a bad idea, for reasons already given. If you own another property, you should be fine: you cannot be prosecuted for "controlling prostitution for gain" unless you are managing her bookings, and you cannot be prosecuted for "running a brothel" if only one WG is using the premises.
As you don't have another property, your options are:
1. Provide accommodation only, no working on the premises. Not sure if you'd get takers, as if a WG is booking hotel rooms to see punters, she could be staying there overnight at no extra cost. However, it might work if she prefers to have some days off and has nohwere else to live, so she doesn't have to pay hotel prices when she's not working.
2. Rent a room in your house to a WG, and also buy/rent another property for her to work from, and charge the WG enough to cover your costs. Might work if she can't get her own place and needs your help - foreign national, no proof of income etc. Possible downside is that she might move on and leave you with a liability for a property you don't need anymore (so renting it might be safer than buying it).
