I guess it's a very personal thing. What might seem completely normal to one individual might not to another. It could be she's embarrassed by gagging and running to the bathroom and doesn't know how to address it. Or it's possible that she doesn't like a man finishing in her mouth and feels uncomfortable. Only the lady involved knows the answer unfortunately. I just hope she answers the OP whether or not she wants to see him again. To ghost someone over a sex act that didn't go to plan wouldn't be very nice. Even if she doesn't want to see him again that's all she needs to tell him.