...it seems unlikely. Knowing the codes of conduct was part of the upbringing of gentry children and I would imagine coming from the household of a clergy father, this would not have gone amiss.

The first time Catherine goes out in the open carriage with James and the Thorpes, it does occur to Catherine to consider the impropriety of the situation but she comes to the conclusion that as Isabella will be along with her brother James, it would be alright: "..who thought there could be no impropriety in her going with Mr. Thorpe, as Isabella was going at the same time with James, was therefore obliged to speak plainer. “Well, ma’am, what do you say to it? Can you spare me for an hour or two? Shall I go?”
“Do just as you please, my dear,” replied Mrs. Allen, with the most placid indifference." (9)

On the second outing, Catherine again looks to Mrs. Allen for guidance after John has tricked her into thinking the Tilneys will not be expecting her to walk with them that day: "Then I will. Shall I go, Mrs. Allen?" "Just as you please my dear." (11) Mrs. Allen is obviously negligent as a chaperone, in my humble opinion. It was such a chaperone/guardian who lacked giving proper guidance which allowed Eliza and her friend to range all over Bath to no good end. I'm not saying that this would have necessarily have been Catherine's fate but it shows the importance of watching out for one's charge/s. If, acting responsibly (and not indifferent), the first time, Mrs. Allen had given her permission, that would have been fine. The second time, she should have at least been reluctant and if she allowed it, she should have verbally, at that time or when Catherine returned home, imposed a stop on any further excursions for the time being.

When Catherine refuses to go on the third outing, she feels to have gone out again would have been improper anyway and "To ease her mind, and ascertain by the opinion of an unprejudiced person what her own conduct had really been, she took occasion to mention before Mr. Allen the half–settled scheme of her brother and the Thorpes for the following day. Mr. Allen caught at it directly. “Well,” said he, “and do you think of going too?”
“No; I had just engaged myself to walk with Miss Tilney before they told me of it; and therefore you know I could not go with them, could I?”
“No, certainly not; and I am glad you do not think of it. These schemes are not at all the thing. Young men and women driving about the country in open carriages! Now and then it is very well; but going to inns and public places together! It is not right; and I wonder Mrs. Thorpe should allow it. I am glad you do not think of going; I am sure Mrs. Morland would not be pleased.(13)

My point in all this is to show that the Morelands would appear to have been taught right conduct. In my opinion James has been hanging around Thorpe all this time and unfortunately has begun to adopt Thorpe's cavalier attitude to some of the rules of polite society to suit his convenience in courting Isabella. At least, this is how I see it. :)