Having one character who is TSTL is bad enough. When both of them qualify, well, you're up shit creek.
Hestia Royce has lived in this small English town her entire life. (We don't know how old she is, but at least of an age to marry.) She knows the power of social approval and disapproval. She ignores that power at her own peril -- and ignore it she does.
And then she blames Leo!
Leo, the missionary who was a teacher before he was a missionary, should know even better. He, too, ignores propriety. He speaks to her without introduction. He goes to her house without invitation.
But she attends the dance at the local assembly room, without a chaperon. And dances!
And she visits him at his lodging, without ever thinking that there might be other people there who would see her and be scandalized.
And he of course compounds everything by admitting her to his room, and then kissing her!
Are these people totally bonkers?
Yes, they are. Because they do all these stupid things without sufficient motivation. This is just plain bad writing.
Now I've reached 84%, and we have more TSTL behavior, with Hestia ranting that all a woman has is her reputation and hers is destroyed. Um, and just who destroyed it?