That's so hard for all the family snowbell.
I am on a biologic treatment for RA and to cut a long story short, my rheumatologist said their assessment is that anyone one One disease modifier should be careful, but didn't need to shield. I used to take the combined methotrexate and biologic but stopped that 3 years ago as post retirement the disease wasn't as active. Plus methotrexate isn't an easy drug to take, left me feeling I had a permanent hangover.
My GP took a different view and I received the shielding letter about six weeks into lock down. I had my rheumatology review over the phone this week. The advice that anyone (like your daughter) on only one disease modifier, methotrexate in her case - does not need to shield.
I suppose the fact her husband works in schools and the children are at school increases your daughter's risk but this situation seems intolerable. If she's otherwise healthy, in her shoes I'd be going home and just being as cautious as possible. She's young, not in the over 70 high risk category so her risk assessment according to my rheumatologist would be 1. Those of us over 70 and on a disease modifier, get 1 for age and 1 for immune suppressant treatment. My rheumatologist says only people who score 3 need to shield.
Your daughter could take advice from her specialist nurse and then make her own informed risk assessment.
Lack of public toilets in towns.