Either they used colored tips and then applied the clear acrylic over them or they used plain tips and used colored acrylic over just the tip part. (you should be able to tell by looking at the underneath of her nail tips)
If they did the former, they may be able to add some white acrylic cover the colored tip, but I am not sure how that would look underneath.
If they did the latter, all they would have to do is file down the colored acrylic with a special drill bit and then apply either a natural acrylic color or white for a french look.
Either way, she should not have to have the entire process repeated.
Hope that helps.