At first I liked Touko, but the way she almost instantly fell for Sayaka's confession when she doesn't have the courage to reply to You is infuriating. Especially considering that she was open with Yuu from the first day and placed emotional constraints on her, but You accepted her regardless.
No matter what anyone says, Touko basically forced Yuu to accept and help fix her (even if unintentionally), and was about to bend for Sayaka because she said she accepted all of Touko when Yuu already proved she did. Yuu is gonna be broken if they get together while they're away on that trip. And Touko will be using Sayaka to feel better for not being able to face Yuu.
Touko doesn't deserve either one of them tbh. Not until she gets her emotions in order, finds herself, knows what she wants to do definitely.