If the point is just to get some initial miles into her account before signing up for a United credit card, she would be able to do that by enrolling in the United frequent flier plan, then registering for their dining program and setting up an account profile. She will need a credit card to do this, but any credit card can be used for this purpose. There is often a 1,000 mile bonus for setting up a dining profile; even if that offer is not available (I haven't checked, though I've seen the offer in the past), she can earn a few hundred miles with one dine.