Try not to break the VAT threshold and dont go VAT registered as the cost will just increase to your clients without any major benefit to you other than claiming VAT back on things.
Different story if you are dealing business to business but I guess you aren’t
Keep records, keep receipts, get an accountant. My account cost me £600 but I paid about £4k less in tax than I saved for or my “tax spreadsheet” came up with 😀
Does she use a room in the house? bills can be offset against that rooms use, laundry costs, uniform costs, stationary, mileage, heating bills (proportional), IT, phone, training, … the list can go on.
When you have a physical business such as dog grooming you need to look after your body and eat more, get massage and rest properly.
good plan.