Any rent increase must not be above the 'market rate', which is defined as what a willing tenant will pay and a landlord will accept for a vacant property. It is usual for a new rent for a tenant in situ to be less than that of a vacant property.
Basically, a tenant has three options:
1. Make a claim with the PRTB that the new rent is above market rate, in which case she will have to find proof of that fact. the landlord will have to have proof that the new rent is not above the market rate. However, this will not take from the fact that she now has an upper limit put in place by SW.
2. Vacate (but she may have to give 56 days notice in writing), as she is unable to afford the property. Such is life, and there are prople losing their homes who cannot afford their mortgages, very little difference here.
3. Talk to the landlord and try to negotiate a lower rent than requested. To her benefit, she has always paid the rent in full and on time. If she vacated, the landlord would have to go to the expense of redecorating the property and after 6 years of occupation without decorating this could prove to be an expensive move. The landlord might also have to upgrade the heating system as well as replace some appliances. All valuable negotiating facts.