The last time I used Fiona as a parent, she treated her kid as an absolute tool, to be used by her as her proxy/puppet with no independence, she was the ultimate controlling mom.
And you can certainly play her that way, although in that occasion part of the reason was that the PC that was her kid was top-ranked in psyche, but didn't end up acting according to his potential; meaning that she was so controlling because he was so disappointing. If he had ended up showing some progress of competency, she'd have eased up on him, no doubt, and started to view him more as a partner in crime.
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And what an honor 'that' would be, a youngling partner of Fiona, direct gene tyes or not, would have to be elder power/experience level at least to be partner-ish with her being of the beliefs they are all her 'lessers'.
I often find that Fiona makes the perfect GM mouthpiece for whenever I want to explain something totally obvious that the PCs/players have somehow managed to overlook. She's a natural for grasping any complex situation even when presented with partical or incorrect information, and she can justify the right level of condecension for the occasion.
As a parent I usually reserve Fiona for those players with an interest in developing powers. If they have some Good Stuff they get Fiona, if they have Bad Stuff they get Fiona. You don't even have to change the way she plays - either version is going to be pushy and demanding, but the Good Stuff PCs get the carrot, and the Bad Stuff PCs get the stick.
And if I'm feeling particularly cruel or rewarding then I'll give them Mandor as a father...