We obviously are discussing a baseless rrat but from my understanding its doesnt sound like she was taking donation outside Phase, but instead getting donation as Yuri as just not reporting them nor giving their cut to PC, my completely made up rrat of how it went down, assuming there any truth to this, is that after the PC funds donation PC asked for their cut, Yuri gave it to them and fish realized it was obviously to little, so he asked for receipts from Yuri she gives them and Fish realized she has been lying to them, then he either told her to pay up what she owns or leave and Yuri either didn't want or couldn't pay so she gets terminated.
(Again I repeat this a baseless .speculation based on more baseless speculation)