You don't have to decide on one college, but you have to indicate which schools you want the FAFSA information sent to (all the schools she is applying to) so you will need to have it narrowed down by that point
I don't know how many colleges the fafsa lets you list these days but I would list all that your dd is remotely considering. all listing a school does is generate a report to their financial aid office so it's not like you HAVE to apply to every school she lists (and since the date for the fafsa is changing some schools who don't do early admission approvals won't even be taking applications yet).