I've had a hard time with Mason and all I can say is that maybe it's best put it off until she happy to sit. If she is crying it's not a positive experiance and you may make it worse.
We've had a toilet sitting routine now for a few months at night. Bath, jammies, toilet with a story and bed. Some nights he has pooed and we fuss and give him a malteser. It's only been in the last week that he has weed in the toilet during the day. He was dry all day on Saturday but today he didn't want to go near it till late afternoon so he wet himself a couple of times. Guess I have to be patient still and not get too excited.