No one has said it yet so....
Welcome to FT!!!
I think you will find very tolerant folks on here, but as mentioned above, if there is a published fee, and UA has been letting you fly without paying it, then consider yourself
very lucky, and dont call UA "stingy" for that reason. There are
plenty of other reasons to call them stingy, but thats not one of them.
I would let it go, plan to pay that fee when you want to bring Fifi (no pun intended) on board with you in the future. If I were UA, I would want to send you a retroactive bill for the many times you flew while not paying the fee.