wow. 73. And depressed?
She could also have dementia or feel she's having issues with her memory which she's too scared to address in case there are consequences. She might not be able to use a new washing machine: too many buttons and dials and things to get used to. She might be evasive in communications and sticking to her routines because that way, nobody notices she's forgetting things and not bathing and nobody drags her off into a home and maybe she just wants to live a while longer in her own house, surrounded by her own things, and if nobody sees her, if nobody notices, nothing happens and she gets to retain her independence and pride.
I know that sounds dramatic, but that's the reality for a lot of older people these days. The state takes their home and their pensions and often they end up in an underfunded government facility with £20 a week pocket money and in an even worse state, both psychologically and physically than she is now. The older ones sit around in the pubs, chatting like conspiracy nuts about it. It's a real fear, for many people, being 'stuck away'.
Maybe she's trying to keep the house or some money so that she has something to give you and the kids. Maybe she's behaving like this, not because she doesn't care, but because she really does and she's trying to keep something to pass on?
I say all this as my FIL, who recently passed away, was as herein described. Not seeing people as regularly. His mates died off. His mobility was suffering, he lived alone, was isolated, and yeah, he knew his mind was going, and he was scared, and he just wanted to live his life, potter about, and go on his own terms, which he eventually did.
He wasn't bathing, had lost lots of weight, had jobs that needed doing around the house and needed new shoes, but none of that he seemed able to do. Everyone in the family was concerned, we'd noticed a lack of food in the fridge, etc, but nobody said anything: too polite, you see. Didn't want to offend him.
Turns out, he had a shoulder injury, couldn't physically get in the bath, couldn't carry the shopping like he used to, didn't want to ask for help in case people started noticing he was forgetful and stuck him away.
We collectivized as a family, somebody did his shopping, somebody else went with him to his appointments, we got a shower to replace the bath and a 'lifeline' call point fitted, all that jazz.
We looked into sheltered accommodation, home helps, support workers: there's a whole raft of people who are able to help with the practical things, but it costs money, and a lot of people just don't have it to 'waste'.
If you're concerned she's not safe, not eating, is exceptionally vulnerable, then you need to phone social services and at least have somebody assess her care needs/mental health status, just in case. You can do that as a concerned relative, and it'd probably be better to tell her upfront, too, so she knows what's going on. She won't like it, but... sometimes, that's how it goes.