It is inappropriate to not tell her that she is dying, as that is withholding important and relevant information.

This is what needs to be done now:

Dearest Charlotte, 

You mentioned in your letter that you and your students care for dying people and that you are teaching your students how to provide a peaceful, compassionate and supportive presence for these patients.

What you said was very helpful. I think this was excellent, what you did. Also, it actually fits with who you and your friend are. You are both ex-hippy, useful guys. Wow – what the ex-hippy, useful guy did at the end of his friend’s life!

Rinpoche advised this mantra to alleviate suffering at the time of death. 

My most dear, kindest brother,Please look at this mantra quite often. Especially look at this mantra when you are leaving this old body. Dear one, please don’t cling to anything, and let yourself be completely free.

Rinpoche gave the following advice on the five powers to be practiced near the time of death.

Generally speaking, bodhicitta. That’s the safest one. But, for somebody who has good concentration, there’s meditation on emptiness.

For your father: read the Prajnaparamita, and make a statue of the Buddha, five feet tall. For your mother: make a statue of Manjushri, four feet tall.