Not in the US. At least not directly to the person. Maybe OK if she is lying dead in a coffin.

She is well preserved. Perfectly alright and common, I would say. Keep in mind that you should write it with a hyphen ("-" i.e. well-preserved as one word) when used as a compound adjective, such as when it is preceeding a noun. Consider the difference: She is well preserved. She has a well-preserved face. That is my preference. I have seen the hyphenated version of the word been used interchangeably with the non-hyphenated version. If you want ta play it safe you should type it as "well-preserved" as this would work in all situations whereas "well preserved" would not.

Hi. Yes you can say he or she 'is well preserved' meaning they have looked after themselves and appear younger than their age .

Hi Sean, yes, you can say someone wears their age well.