Yvonne, hi thanks for the candid note, this is a very good example of why landlording/PM'ing is not as straightforward as people like to make it out to be. There is a human aspect to it and its hard to not be affected by that.
First thing, you titled yourself Property Manager, which you are, but are you also a licensed broker in NC? If you are make sure you have your ducks in a row with respect to SecDep laws etc. these folks sound like they could be a nuisance.
In either case, I would trust your gut. If you think they will be a hassle and continue to pay late when they feel like it file for eviction AND close any channels they have to pay you rent. You don't have to accept their payments (checks, M.O.'s) but if they direct deposit they can make a small deposit and it will be considered accepted and nullify your case.
Also, make sure you are charging a late fee 5% in NC that seems to motivate people as well.
Its a tricky situation and likely won't end with rainbows and unicorns but the sooner it ends the better. As a bonus, this is a much better time of year to be finding tenants vs. November!
Yes, the involvement of your daughter is disturbing and totally not OK, I would tell the Mother (owner) that this behavior is unacceptable and if she is not sympathetic then don't worry about burning that bridge, it wasn't worth crossing.