...could of just worn the Tshirts inside out. Print wouldn't be so obvious
Maybe. If the decals are made of stitching or are any kind of pressed plastic inlay it'll still be visible even if worn wrong. Worse case, the shirt is reversible and has a lewd design on the other side.
On the other hand, dressing shirtless with breast harness isn't even appropriate for regular public to say nothing of school. How did she convince herself to even open the front door completely exposed like that? Plump succubus is cute in that outfit though.
There's also "Why did she wait until ALL her clothes were dirty before washing them?", "She doesn't even have some old clothes in the back of the closet she doesn't normally wear anymore?", "Why not just wear some still-damp clothing, and let body heat dry them?" or "Why not just go out and buy a t-shirt to wear for today?"
Depending on how damp the clothes were (assumption: not having an electric dryer), you can catch a cold rather easily wearing damp clothes for half a day with the air conditioning on. There's a reason it's standard operating procedure that if you get caught in the rain, you get in the shower and a change of warm clothes as soon as you come home.