I agree with all you say of Marianne. But when you say they are both scripted it got me to think about it.

Do we know that Mrs. Dashwood's behavior is scripted? I tend to think she's more naturally overly emotional.

Returning to Ch. 1 a minute
of Elinor
and her feelings were strong: but she knew how to govern them: it was a knowledge which her mother had yet to learn, and which one of her sisters had resolved never to be taught.

Sometimes their behavior appears the same (ex. creating sorrow again and again), but not always. We are not shown Mrs. Dashwood going around speaking poetically of leaves, and she doesn't seem to require other people to behave in a certain manner like Marianne does.

She seems to discern Elinor and Edward's attachment without requiring exact displays of attachment. Yes, she jumps to conclusions about what that means.

Here are a couple of quotes from Mrs. Dashwood that show a distinction between her and Marianne.

In Ch. 3, after Marianne laments at Edward's tame reading and lack of real taste, Mrs Dashwood says
"He would certainly have done more justice to simple and elegant prose. I thought so at the time; but you would give him Cowper."

And in Ch. 8, Marianne thinks Edward must be ill, because that could be the only reason he hasn't visited them yet.

"Had you any idea of his coming so soon?" said Mrs. Dashwood. "I had none. On the contrary, if I have felt any anxiety at all on the subject, it has been in recollecting that he sometimes shewed a want of pleasure and readiness in accepting my invitation, when I talked of his coming to Barton. Does Elinor expect him already?"

Indeed, I think Mrs. Dashwood is the more perceptive of the two. Don't you think it's strange that Elinor explained her fears to Marianne and she basically ignored them? We are not told of Elinor confiding in her mother on this point, yet Mrs. Dashwood does perceive something is wrong.

Perhaps the difference is subtle, I just thought I'd throw it out there.