Potty training

We're introducing potty training but we're not serious about it, at all. She likes to sit on the potty and read books, sing songs, etc. I ask her if she wants to go and if she says yes, we sit on the potty. If she says no, we don't. The issue we're running in to is that if she DOES pee while she's on the potty it scares her and she cries hysterically. She's only gone pee on the potty 3 or 4 times but every time she does it she's reacted this way. Any ideas or tips on how to handle it?