This is a link to an extended Gagg Family Tree, covering various counties and Countries and includes Gloucestershire.
It may be worth sending the owner an email asking if they have any information about Betty.
She is listed in the Gloucestershire Family Tree, but no information about who she married (which we know was Richard Vaughan). It may well be that they have new information but haven't updated the Tree

http://www.alangagg.f2s.com/

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Finding new ways to spell Vaughan every day!