Is it appropriate to ask for a recommendation from my boss?

I’m applying to graduate school, and the application plus the references are due in April. I started an internship in January. My supervisor works in a different office in the next city over, so I don’t get to see her very often and haven’t really had a chance for her to get to know me that well. I really really need a recommendation from her, but I’m afraid it’s not appropriate to ask because I haven’t had much of a chance to show my competence or values, etc. I've only really met with her in person 3 or 4 times! Should I ask anyway?