I think if you sit her down somewhere where you have privacy, take her hand, look her in the eye, and say you are concerned about her, and because you are concerned about her and care about her you want to ask her a personal question that might be embarrassing. Is it okay with her, if you ask. She will most likely say yes. Say, she's mentioned several times about her new medication making her constipated. She's also seemed to not feel very well. As she may or may not know, an enema or two might help with that problem. She also may or may not know that you are a very experienced enema giver, and you'd be happy to help you with this ongoing problem if she'd allow you.
You think the world of her and would never want to upset or embarrass her but are very concerned about her and want to help. Your knowledge and experience with enemas leads you to think that getting one would help immensely and having them regularly would help prevent her constipation problem. You might even mention she's like a daughter to you and this is what you would do for your daughter if she was having the same problem.
If she is truly angling to for you to give her an enema, she will jump at the chance to either get one, or to talk about it. You can also let her know if she's too embarrassed to get one from you due to your friendship, you'd be happy to find an enema clinic to administer one to her. However, you think she'd be better off in your care. You can point out that if something happens the next day or later, she can always come to you for help and advice. That is actually a pretty big item for a newbie.
I say this because I reached out via PM to another member who was a colon therapist when I had some problems after receiving an colonic at a clinic. He was able to alleviate my concerns and let me know what was happening.
Let her know you care and want what is best for her and you are there for her no matter what. If she says no, you can say that's fine. If she changes her mind she can always come to you anytime. You are there for her. Trust me, she will be very touched at your willingness to approach the topic with her and your evident care.
If nothing else, it may plant the seed in her mind.
Crossing my fingers for you.