I have a covid precautions factsheet that I send to all clients prior. For those who don't have whatsapp I give them the gist over the phone. It basically explains the PPE I'm wearing, the surcharge for PPE/sterilising, etc. It also has on there:
If they or anyone in their household develops covid symptoms (list symptoms, explain that a continous cough can be 3 or more coughing episodes of over an hour in 24 hours), (note SYMPTOMS, not a positive case) 2 weeks before or after their appointment they should contact me immediately.
I've also put a bit about how my cancellation policy of 50% charge for appointments cancelled unnecessarily within 24 hrs does not count for covid symptoms, health issues are a necessary reason.
However despite your best efforts it does come down to being shrewd and cautious. Last weekend I rang one of my elderly clients to double check she was ok for her appointment on Monday. She said yes then whilst being chatty told me 'she had gone to hospital for a scan a couple of days ago and has had an awful cold ever since'
I gently tried to ask if she had had the covid test but she was adamant that it was just a cold. So I said 'well how about we rearrange your colour for (2 weeks from then, thinking if by any chance she has it she won't be contagious by then) as it's a longer job and I don't want to tire you out, especially as you're not feeling well' etc etc. She was absolutely fine with that and even thought it was a good idea!
I think it will be fine as she has carers anyway so I'm sure if they thought it was covid they'd make her get a test, but it never hurts to be safe than sorry.
Finally something my long-suffering Mum would say when things have happened to me: Don't stress out, YOU DIDN'T KNOW SO DON'T FEEL GUILTY, it's in the past, and learn from the experience.
....'Yikes I really am turning into my Mum...'