The problem I think alot of rule followers have is their condescending attitude towards those who are maybe disinclined to follow the rules. Others love to martyr themselves for "the greater good" and are often quick to point out how much they have suffered for the sake of the rules.
I don't steal food. We can all agree its bad to steal in general and that if people were to steal en mass it would have a massive negative impact on society. You can be sure if my child was starving I'd steal the food out of other children's mouths if it made sure my child got something to eat.
Our ability to care for the greater good, or wider society as a whole is dependant on our current position at any given point in time.
In your friends case, if her mother were to catch covid and die, then it would be something she has to live with for the rest of her life, but her and her mother should be free to make that choice and risk if they feel it is worth it.
She could follow the rules and her mother could die of an unrelated stroke, or something else that strikes at random, out of the blue in February. I don't imagine the fact she followed the rules and "did her bit" will give her much comfort in that situation do you?
I believe, and is only a belief, your worldview may see things entirely differently to me, that most people won't do whats best for society out of choice, especially when there is no real punishment for not doing so. Most people only comply, with rules in general, because the cost of not complying outweighs their perceived benefits.
If they had roadblocks on the motorways and police at train stations checking where people are going and why, with actual punishments enforced, then you'd have a near total rate of compliance. Would you want to live in that world though? I wouldn't.