Please keep in mind that there are a lot of things that can and maybe should be bought in E”Y because they could use the parnasah and YOU are paying extra for additional luggage anyway or being matriach other people to shlep your kids stuff with them. I am not saying this to be rude or negative I am just saying it as a thought.
Also many people forget that E”Y goes through seasons as well and it does get cold there so be prepared for that.
Kids do have access to laundry and they don’t have much room or closet space so you might want to discuss that with your daughter and seminary to see if it pays to send more to do laundry less often or send less and more $$$$$ to do laundry more often. That depends on the seminary and the accommodations.
If the seminary has a uniform/dress code you will have to conform to that and buy clothing accordingly. If not, then you are on your own where that is concerned. Girls should really ask other girls what they used the most and what they brought that they hardly used at all. Such as sneakers and flats. They definitely need more than one pair of each.