Age can be a factor, as can general health and medications.
If she is under a doctor's care, I'd suggest asking first.
Also, if taking medications, I usually suggest a person not take cleanse products within 2 hours of taking meds.
If she is in otherwise good health, there are still things to look at such as water intake.
If she's not willing to up her water intake, a cleanse may not be as effective as she would wish it to be.
I feel preparation and understanding about cleansing is as important as finding the right cleanse.
I'd start at a time when she has a day or two to take it easy, not when she's going to have engagements, appointments, etc.
I'd stress more water intake, moderate exercise to help the colon be naturally stimulated...stretching is great, provided she is in good health to do so.
Eating light and healthy during a cleanse definitely helps. Lots of fresh fruits and veggies, no fried foods, white flours, refined sugar or red meats.
I know of a couple of really good cleanses but am unsure about posting information here so if you want that info, just email me or visit my profile for my site info.