Well Lee, there are a couple of ideas that spring to mind.
Yes, it's possible Maude could have been adopted by an uncle & aunt but adoption records would need to be found to confirm that theory.
On the other hand, it could be that Rebecca Jane was married twice. She may have been, for example, Montgomery before she married a Livingstone and then if Mr Livingstone died, she then married Samuel Bell. This could account for why you are finding both surnames cropping up. It would be interesting to see if there is a birth record for Rebecca - do you have any idea of her year/country/area of birth?
Lastly, one question. Where does Florance Bell come into it? Was she an aunt? And if so, do you know who she married?
Don't know if the suggest above is of any help?
Kay
Manager