With the elderly, I have found that you have to go very slow with them in explaining anything new. They don't want to believe that anything they believe/think is wrong or needs to change. You have to kind of coddle them and get them to trust you, and then they might try one thing.
If it was one of my parents' friends, I would be extra sweet and assuring, using all the patience I had. I would ask them to get a pen and paper so they could write the instructions down. I would tell them what I was about to tell them, I would tell it, and then I would tell them what I just told them. I have to do this with my father-in-law.
Every elderly person I know is very medically oriented. They have been taught to trust doctors, and they just don't know about any alternatives. They get scared easily, to the point of paranoia. They really have to have their hand held a lot.
Not many elderly women are going to want to do enemas. The fact that she can only get the enema tube in one inch tells me she is tense and scared. She doesn't have a mental picture of what the rectum looks like on the inside, and she doesn't want to puncture anything. Plus if she has blocked nerves, she can't feel what she is doing anyway, which might even make me nervous. Having a nurse or someone in the bathroom with her or doing it for her might make her more comfortable.
I think I would tell her, nicely, that the diet she has been eating for 60 years is what is making her get so clogged up, and it clogged up her relatives, too. I would offer really easy recipes that she could try. With my father-in-law, he would be willing to eat almost anything, but he doesn't cook and doesn't know his way around a kitchen. So he just buys frozen dinners. I have made smoothies in the blender for him, which he loves, but he won't do it for himself. He will eat a little side salad, but he wants his meat, potatoes, gravy, 2 cooked sides, and pie and ice cream for dessert.
I would ask the dear old lady if she would be willing to drink more water. I would tell her to put it in a half gallon pitcher in the morning and make herself drink the whole thing every day. Tell her why this is important. If she's wealthy you can tell her how everyone's drinking bottled water now. But if she is on a fixed income like my father-in-law is, she will probably only drink bottled water if someone else buys it for her.
Money is more than likely the issue behind the "I'll have to ask my husband" comment. If they are watching pennies, and he controls the purse strings, then she does have to ask if they can afford to do the enemas or anything else.