Potty training help!

So I’m starting to potty train my daughter today. I put her in regular underwear and she cried a little bit and was fine. Then she peed and obviously she got all wet and it got all over the floor and it freaked her out and she started crying for a diaper and went to go grab one and give to me . Is this normal behavior? Should I keep putting on the underwear or do you think she may not be ready? I’m trying to explain to her she needs to go to the toilet and pee and she won’t get wet but she doesn’t want to it seems like. She sits on her toilet when I go to the bathroom usually but doesn’t want pull her pants down. I know she watches me and gets the concept and she already goes to her toilet and says pee pee poo so she knows what it’s for so I think she should be ready but idk it seems like she wants to be in her diaper! Any tips ladies??