I think that anyone who has followed the path of radicalisation needs to be extremely closely monitored for a lengthy period, if indeed allowed to return to this country at all.
I think that terrorists may lie about their circumstances and motivations in order to position themselves in places where they can launch attacks or facilitate those who will launch them.
I do not see any reason why a woman should be believed simply because of her sex; and I suspect a young man who had voluntarily left UK, trained with terrorists and then sought to return to UK (following unprovable circumstances leading to apparent volte face) would face a similar level of investigation.