Can I ask why you need Lasting Power of Attorney for your mother? She clearly has physical diagnoses, does she also have mental / cognitive issues? If you are aged 20, then I can’t think she would be very old herself, so a POA might be a bit early, unless she is incapable of making either health or financial decisions for herself. (There are two types of Lasting Power of Attorney, one for Health and Welbeing, the other for Property and Finance. A person may have one or both or these.)
An advance directive on the other hand is a very personal thing. It states personal wishes in case of certain situations. It’s quite unusual for someone else to suggest an advance directive, given that it is all about personal views.
I personally have an advance directive. I decided I wanted my views to be made very clear in any situation where treatment might be needed to keep me alive and I would rather not be. I have sent a copy to my GP, keep a copy with my will and have discussed it with my friends and family. My husband supports my decision, but does not have one for himself.
I don’t have a POA, nor do I think one is needed. I may have long-standing MS, and some cognitive deficits, but at this point I am quite capable of making health and financial decisions for myself.
My husband and his brother have POAs for their mother, who has dementia. In that situation, it’s quite necessary as she no longer has the capacity to make either health and welfare or financial decisions for herself.
If your mother does need someone to have Power of Attorney for her health and welfare and/or property and finance, then you should probably have the discussion together with another person present, preferably someone whom your mother trusts, perhaps another relative? That way it won’t seem as though you are being overzealous in your care for your mother. As Kay suggests, getting another, older, friend or relative involved might make the conversation easier.
By all means you could explain what an Advance Directive is, but it’s something that only a person with good cognitive abilities can or should do.
I wish you the best of luck in arranging things for your mothers wellbeing.