Co-worker question

What do you think is the best way to handle a co-worker who repeatedly questions you? Part of my job involves booking
appointments for my co-workers. One, and thank God only one, of my co-workers consistently asks me, basically, why I’m not booking her more clients.
I really am doing my darndest but some clients don’t want her or they want a time that she won’t accommodate. Instead of recognizing this, she just keeps questioning me, like I’ve done something wrong. I’ve done my thought work on it, realize she gets to be who she is and she’s questioning me based on her own wrong thinking, but, of course, I can’t “self-coach” her, only myself! I typically remain patient with her but I feel like my patience has enabled her to continue pushing my boundaries. I say to myself, how do you want to show up here? I take pride in my work, so it’s unpleasant when someone consistently questions me. I’m at a bit of a loss for a peaceful solution. I’m thinking all I can do is accept her as is by not keeping a manual for her on how I think she should be and find a good bridge thought to keep me from smacking her…maybe, I don’t like her behavior but she gets to show up however she wants while I choose thoughts that serve me. That’s not really inspiring me:(
Any thoughts?
Thank you!