I have it too and other conditions, it does make like difficult.
Social Services (apparently going through the GP is better as I got nowhere with them) or private carers.
I am sure there are some on here who do that kind of work to give you an idea.
Woofgang might also be able to suggested a starting point of where to look.
If you are near Cardiff Uni then worth checking if they have a volunteer section (my Uni did and I volunteered with them) if any of them could help with some bits on a more adhoc basis or as a companion, maybe do some things like shopping, errands and little bits of housework but they, of course, will not be trained and not sure how any insurance would work.
Might help to get an idea of what help it is she needs, more companion like, shopping, housework, meals, personal care, any lifting, washing, bathing, dressing etc... as that could make a difference, also whether finances would have an impact on what care can be received for what cost.
Maybe there might be some local community events going on, where people get together for a coffee or chat, if there is provision for her to be collected and dropped back off so she isn't on her own for the whole three weeks. Maybe a local fibro support group might know and be able to help with some company?