You are doing it right. If she walks away let her give her time to come back up. I imprint mine but I only do it for the first week and then I leave them alone to be a horse. I normally don't do much until they are a yearling and still find they remember what I did when they were first born. This approach works best for me.
I am not sure if I would work her 10 minutes she is a baby and she probably isn't retaining a lot. Instead work her for 5 minutes. You are doing good just keep it up. Don't burn her out if she doesn't want to come up don't make her.
Something else that you might want to do is at least one of those times go out pet her and let it go at that. That way that she doesn't start associating you with work all of the time. She could start resenting to see you because she knows that when you come down there to see her that it is always work time and not just pleasure time.