It’s really not necessary for her to tour schools before applying, whatsoever, and even less so now, what with virtual tours. The notion that she should fly to the US and jeopardize her A-levels, to tour schools that she may never get into, to decide where she wants to apply, is just ridiculous.
She (and you) should do your research online beforehand. If she has absolutely NO idea what she wants to study, then she should focus on large schools with many available majors. If she already has a specific major in mind, then she should focus on schools that match her qualifications and geographic preferences, and offer the major that she wants, that have strong departments in that major. If she knows that she wants a small school environment, and it has the majors that she likely wants, then narrow the list that way. Does she want to be in a big city, or on a suburban campus but within striking distance of a big city (and I should tell you, most college students wind up not utilizing the nearby city, but just stay on their suburban campus), or does she want to be at a rural, isolated campus? What climate can she put up with? What level of local city crime are you willing to take a chance with? Are you limiting her to the East Coast, or are you willing for her to have to take two, maybe three flights to get home
As you can see, once you apply these selection criteria, you’ll probably be able to have pared down your list to a dozen or so schools, and that’s where she applies. Then, AFTER she has been accepted to schools, once she knows her final list of acceptances (and maybe wait-listed schools, too), THEN in early April you have her come look at the schools, and have her decide which one she wants to go to, and possibly rank her wait list choices, too, just in case they offer her a spot over the summer.