The obvious source is the Register of Electors. The vote was extended to all women in 1928, so she should be listed from then onwards. Start with 1948/9 and work backwards.
The snag is that the Register of Electors cannot be consulted online. You would need to go somewhere that has them in hard copy, or get someone to go on your behalf. There are copies in Edinburgh and in Aberdeen, and it is possible that the library in Banff might also have a set.
The usual, and unambiguous, way to set out the name of a married woman is 'xxx yyy or zzz' where 'xxx' is her given name, 'yyy' is her maiden name and 'zzz' is her husband's surname. This is the form mostly used in legal documents in Scotland, where a woman does not legally lose her own surname on marriage.