I had a similar thing, which led to me firing my long-term SLF pilot.
She started off Harmless, had ranked-up to Dangerous and was taking, IIRC, ~10% of my profits.
According to her bio' she'd earned Cr170m.
Now, I do okay for credits in ED.
I'd made quite a few credits recently (and spent 'em on upgrading my 'vette) and I completed the Ancient Ruins mission but, even so, I doubt that I've made Cr1.5bn this year so I'm not sure where she got that Cr170m.
What's more, for a while I was deliberately taking her on missions with me, to let her rank-up, and during that period I was paying attention to her stat's and she'd only earned around Cr30m.
After that, I decided on a bit of a change of pace so I've been spending time doing things like unlocking engineers, gathering mat's and upgrading ships as well as investigating some lore-related stuff - none of which is especially well-paid - and yet that's when she seemed to have earned the remaining Cr140m.
One thing which occurs to me is that I flogged a bunch of my unused ships and modules recently (to fund the upgrades to my 'vette) and I'm wondering if she took a slice of those credits too.
Which would be a bit of a rip-off since she would have already taken her slice of the credits I earned to BUY those ships/modules and taking another slice of the credits I received when I sold them again would be double-dipping.