I've namechanged for this as I would hate anyone to identify my friend.
Background is that my friend's DH is a super high-earning overachiever. They are quite old parents of two primary-aged boys, one of whom has quite significant SN. My friend is a SAHM with a lot on her plate (for reasons I don't want to go into for reasons of identification) and absolutely no family support whatsoever. Both she and her DH are demanding types, both on themselves and on others, with very high standards in everything. I think they made some sort of pact not to ever have a nanny; she manages a large and very glamorous home, with lots of entertaining (including long-stay guests) with the help of a PT Filipina. She and her DH are currently at breaking point, both accusing the other of not being helpful or supportive enough. Her DH cannot cut back at work for another three months (and even then it won't be significant). He is well into his 50s and often goes to bed at 3am, gets up at 6am etc. He needs to rest more, and he needs to stop expecting his DW to pick up all the pieces all the time (and she does, brilliantly, but is at the end of her tether) and not complain that she isn't available enough. She needs time off for herself, and for him.
I have hinted that she needs to accept that she needs more help with her children so that she and her DH get a break for even half a day at the weekend, and she makes lots of excuses. She finds it very hard to let her children go - neither of them have ever slept away from home without their parents. But I fear that her marriage is at stake, and her DH's health is definitely in need of care. What can I say to persuade her that she and her DH don't have to be there every single second of the day for their DCs?