It's interesting if you got to the Shula's website I've never found a thing about dress code. If this were non-COVID times you might feel out of place, but there are no conventions going on so I think your daughter will be fine, but if you want to swap her t shirt out she might feel better. If you want, drop them an
email and ask. If you look at the
photos on the Swan/Dolphin site you can probably judge for yourself. On OpenTable, it states "Business Casual" - this is their official reservation system so that's about the most accurate I've been able to find.
Here is what the the DisneyFoodBlog it shows;
Dress Code: Dress Code Guidelines:
Men: Khakis, slacks, jeans, dress shorts, collared shirts. Sport coats are optional.
Ladies: Capris, skirts, dresses, jeans, dress shorts.
Not permitted in dining room: Tank tops, swimwear, hats for gentleman, cut offs, or torn clothing. While T-shirts are now allowed, the policy remains that T-shirts with offensive language or graphics are not acceptable.