Two off the cuff questions.
- On Github, in her Profile > Emails section, does she have an email marked as Primary? (if not, have her mark one as Primary)
- Does she have “Keep my email address private” checked? (if yes, can she uncheck it?)
Last thought, while at her Profile, have her go into Authorized Applications and revoke the access for your Discourse instance. That way it will request that access again at her next signin attempt.