It would be a lot of work, and the entire garden meanders around the house itself, on sloping ground, so for older people it would be a little harder to move about and cart things around. I understand why she cannot maintain it.
The remoteness of the property makes it difficult for volunteers to come as regularly as needed, the cost of fuel would be preventative to most, especially considering most volunteers would be older people, retirees. Sad for sure. I'd do it if I was able, stay locally, do a couple days a week, but I don't have that ability right now.
Oh... I do understand how things are not as doable with aging. I only have flowers around the deck and in some pots, the smallest amount ever for me and it still takes a lot to me to keep them nice. Some time back, it would have seemed like nothing.
Like you said though, the bulbs will still come up and the the trees will still blossom for years to come.