Xanax and Adderall mixture?

[Madison]

I'm worried about my sister. She is prescribed to Xanax and Adderall- she is told to take one 2mg Xanax pill 4 times a day and also one 30mg Adderall pill 4 times a day. Does that not seem like a lot? I've never heard of anyone being prescribed to that much Xanax. She is only about 110 lbs so I'm definitely worried that strength is just too much for her. Also, Xanax is very addictive and if she is on that much every single day then it'll be no time before she is hooked (she has already suffered from drug addiction previously). Her doctor is in Malibu, CA so I'm worried he is just one of those doctors that will prescribe unnecessary amounts of drugs (like Anna Nicole Smith's doctor and others like that).
Oh and she is also prescribed to Ambien for sleeping so she takes that daily.
I've told our mother about how much medication she is taking- even though my sister is 24 and I'm 20- I feel our mother needs to be aware.
What do you think about these strengths and these together?