So at a high level, this is a combination of preferences that is making the cost issue fairly hard to solve. Not necessarily impossible, but looking at smaller research universities and LACs like Swarthmore, on the East Coast, often means you are looking at private colleges which mostly focus on need-based aid, because the desirable location means they do not need to offer much if any merit aid.
On the other hand, if she was willing to stay somewhere in the Great Lakes/Upper-Midwest, then way more such colleges offer serious merit aid, because they need to in order to compete with their coastal peers.
So I can’t comment on theater, but in terms of good “science” LACs, with good grad school placement, that offer merit, there is Grinnell, Macalester, Oberlin, St Olaf, Kalamazoo, Lawrence University, Allegheny (technically not Midwest but Western PA), the College of Wooster, Knox . . . lots to look at. I don’t know all those in detail, but I know many have excellent study abroad programs.