Do not touch them with a barge pole! Please.
Beside it being illegal (!!!)... if something happened to your child (God forbid) in her care, she has no liability insurance etc. There are processes in place for childminders and we adhere to them for good reason.
You would also have no one to complain to/backup support system (OFSTED/NCMA etc.) if you werent happy for some reason.
Basically, as nice as she is... she could just do as she likes...
Plus I (as a registered childminder with an outstanding grading...) always insist my prospective parents phone as many refs as they like... and I give about 8...character and work refs. One ref is just not enough imo. Even tho OFSTED are happy with me... I am a big believer in refs.