One of the interesting things that is going on through this book is that Catherine Morland is getting a sentimental education. The books she is reading are teaching her how to respond. And sensibility is all about responsiveness.
Think about stress, which is a modern word we use to describe one kind of sensibility. Suppose I want to reduce my stress. What can I do? One approach would be to avoid stress causing situations. I'll give up driving, change my job to one with less pressure, avoid people whom I diasgree with &c.
Another approach is to treat the way I react. This approach says that stress is not the car that cuts me off on the road but the way I react to it. Now I can't just decide not to get upset. What I can do is train myself to respond differently. Every day I can slowly train myself not to shout at other drivers, not to get riled up. It will take work but it can be done.
Sentimental education works a lot like this and one of the things that is going on in the background is that Catherine's reading experiences are training her to respond in certain ways.
What is interesting in this book is that we learn far more about the sorts of sentimental education that are not helpful than the kind that are (we have to wait for Sense and Sensibility for the latter).