It's throwing the blame from one to another.

What we've got to do is to find out the real guilty person, and that's not going to be easy, I'm afraid." Ulyth sighed and wiped her eyes.

She had been deeply hurt at Rona's sudden attack.

It is humiliating to find that where you occupied a pedestal you are now, even temporarily, a broken idol.
"She's right to scorn me if she imagines I'm such a sneak, but how could she suppose I would?
And yet I thought her guilty.

Oh dear, it's a horrible muddle! How shall we ever get it straight ?" Ulyth sat thinking, thinking, and was no nearer to a solution of her problem when she suddenly heard the brisk ringing of a bicycle-bell on the road below.