Is your daughter worried about not having a therapist? Sometimes for maintenance, meds are sufficient, and the stimulation of a new environment heads off depression for awhile too.
You haven’t given much information on the program she will be in. Is it structured and staffed by the originating school here iin the US? Is there a group going, with people she already knows? Will she be in a dorm, with a family, or off campus on her own? What resources for counseling or support are provided either by the US school or the French one? Etc.
One of my kids has a seizure disorder. It felt risky when she wanted to go to Europe to do grad work. But I reasoned that if she stays absolutely safe all the time, her life will suffer. Most of all, it was up to her.
Since she wanted to do it so badly, and is a mature person, I resolved not to show too much anxiety and project confidence in her plan. Logistics need to be checked out but overall I would maybe tell your daughter that she might do fine on meds without her current therapist, and ask her to find out who she can talk to if she does run into a spot of trouble, in the new environment. But convey your faith along with being available if problems arise: a tricky balance.