She can sing that's for sure, I just watched her on a news show, she did amitt the show came after her... she did take singing lessons once a week for quite some time in her thirtys. So is she truly an amateur,or a trained singer??
As a musician myself, I think it is perfectly acceptable to consider her an "amateur" even though she's had voice lessons.
How many golfers have taken years of golf lessons but have never played in a PGA event?
How many TDR members have taken courses in auto mechanics or sat through workshops at a TDR event but they are still "shade tree mechanics".
Who's taken cooking or baking courses for the enjoyment? Doesn't mean they are professional chefs.
That's what continuing education is all about. Identify a talent or strong interest (hobby) and learn more about to help your enjoyment of this interest.
Can this lead to a professional carrier? Sure! That's not a bad thing.
In Ms. Boyle's case, she has a fantastic voice. If she has some acting talent also, with this exposure there's no reason why she shouldn't end up on a stage on Broadway or London, Toronto or any other big theatrical city.
There are plenty of musical theater roles she could be cast for:
Music Man - Marian's mother
Fiddler on the Roof - the mother or the match maker
Oklahoma - Aunt Eller
Wicked - Madame Morrible
Sound of Music - Mother Abbess.
... to name a few.