Vaginal Estrogen for Incontinence

I have a friend who is struggling with incontinence and it's getting much worse. I don't know if it's due to her diabetes, her weight gain, medications she's on or if it's due to menopause.

I wanted to suggest vaginal estrogen to her since I just read about it for the first time the other day and many women raving about how it helped their incontinence.

I have some questions before I feel comfortable suggesting it to her.

Has it been studied and proven to be safe and not cause reproductive or breast cancer, heart attack or stroke?

Is its use fairly new or has it been prescribed for many years?

Is it prescribed by mainstream doctors or is this something that's seen mostly coming from alternative/holistic practitioners?

Does health insurance cover it?

Has it helped any of you with your incontinence or given you any bad side effects?

Thanks a lot for any information or answers can give regarding this.