If your veterinary trainer-trainee relationship isn't working, consider the following advice and get back on track:
Have a nonconfrontational chat. Start by saying something like, "I'm sensing that you're feeling overwhelmed out there and I want to make sure we're a success. Don't be afraid to tell me what's going on." Pay attention to body language as well as verbal communication—after all, a new hire may not want to come out and say she thinks her trainer is terrible. Ask if your style of training isn't working for her, or if there are factors outside work that are affecting her performance. Make sure she knows she can confide in you.
Offer gentle but honest feedback. For example, "Mary, I'm noticing you aren't recalling a lot of the information I've asked you to study. Are we moving too fast? Do you do better with auditory learning? Or has something kept you from studying?"
Try a different trainer. If you've taken the previous steps but your trainee still isn't succeeding, pair her with a strong team member who isn't like you and see if they make more progress. If so, you as the trainer are getting in the way.
Have a serious conversation. If the above technique fails, get tough. Say something like, "Judy, I need to be honest with you and let you know that right now I'm concerned that we aren't making strides in your training. Is there anything we can do differently to help get you on track? You aren't going to hurt my feelings—my goal is help you learn."
Be careful not to judge a new hire too quickly, and consider this: successful people often have a lot of confidence and can be overbearing to new hires. If this process comes up more than once or twice in a few years, take a hard look in the mirror.