Is your daughter resilient, adventurous, independent, thrives on adversity? And does she know exactly that what she wants to do and why?
These qualities would be needed for her to not just get a free education, but to enjoy herself and thrive.
The article linked is a start, but a bit misleading in the students portrayed. Grad students are considered grown ups on both side of the Atlantic, and grad school is only for a year or two.
Moving to Germany, at the age of 18, just after high school, is different.
German students don’t “go to college”. They aim to get an education or training in a very specific subject, and before they think they know what that is, they don’t go. If they change their minds and aim for an unrelated subjects they have to start over.
University students in Germany are not considered “kids” - not only because they may be somewhat older in fact, bit they are not expected to need support, handholding, tutoring. Most of them live on their own, they have been drinking legally for years.
“Very little support” means so little it wouldn’t even register for a US student. If you are having trouble in a subject seek out a professor in their office, chances are high that at the professor won’t be there at all, b) the professor is there but the secretary won’t let you speak to him (very occasionally her) or c) you manage to meet them and state your problem and they will tell you, more or less politely, to pick another subject.
Few universities will have a campus to speak of, and housing will be spread all over town. German students are used to seek out their extracurricular activities in the community, specifically sports.
If you rely on “picking up the language”, your social life will be very limited and every interaction outside the English speaking classroom fraught with difficulties.
If your daughter Is someone who loves a challenge, who has a clear path in life comparable to a grad school student, this might work for her.
I’d also add, though this advice may be somewhat outdated, that I would recommend Germany only for STEM subjects or fina arts and music, and would look very. Carefully at the school.