Remember that she is a grown person who is entilted to make her own decisions
By legal definition, yes.
In terms of wisdom, maturity and (perhaps most importantly) foresight; most girls enter this very tough,
very life defining business at what age - 18, 19, 20, 21? My idea of what 40 was going to look like when I was 20 was hazy and then some, and I don't think that's the least bit uncommon. Forty seemed like an eternity away. Often these young girls get involved out of pure rebellion. Or they get seduced by people that aren't interested in anybody's well being but their own [producers with dollar signs in their heads - meal ticket boyfriends - etc] who sell them an innacurate bill of goods about the fame, riches, glamour and glory that await them in the biz.
If I saw my sister headed down that road I'd definitely make a concerted effort to dissuade her.
because god knows that I wouldn't want her "butting' into my business.
I wouldn't like it either; not a bit. But no matter the amount of butting, the final decision would still be mine.
If her influence helped prevent me from making a decision I'd have looked back on with great regret, then in retrospect I'd be thankful.
In my experience, the fact advise is often unwelcome doesn't mean it's always bad.