I will state my opinion although you may not like it. I will write it anyway, feel free to ignore it.

From reading your other posts I've got an opinion that you have some issues around money. If I remember correctly then the theme whether your T is worth the money you pay her as been constantly on your mind. So, in that sense there's no wonder you are contemplating the issue of taking back the check - considering the whole context it seems perfectly natural and normal.

What I find alarming though is that your T does not charge you her full fee although you both know that you can afford it. And moreover, she was offering to give you back the check for the time and service she had already dedicated to you! I don't know what it means but somehow it seems that she is subconsciously either afraid of you or somehow joins you in your pathology, fostering dependence and preventing working through the related issues.

If she would be strong enough to demand you her full fee (because as you said, you can afford it) then this problem of yours, that you feel she does not deserve your money, could come more fully into open and who knows what lurks behind it. Right now it seems to me that the T herself is preventing really discussing those issues.