Gregory's Server
Critical question: is she actually sending these emails from within the Gmail UI (app or website)?
If she's sending mail appearing to come from her Google-hosted domain, but actually sending them through another route (mail app going to ISP's mail relay, firewall at work/public routing SMTP to its own relay, etc), then the mail she is sending will be violating her own SPF and DMARC policies (if they're anything but wide-open).
And that means they're invalid, and go to spam.