Shouldn’t think you need worry!

[Coffee Break]

I encountered the expression "Shouldn’t think you need worry!", but am finding it difficult to understand it. Could you please let me know what it means? Here is the excerpt:

An arm slipped round her waist, and made her jump.
“Sorry I’m late!”
“Hullo!” said Mary. “You’re—you’re not late.”
“I say—what a stunning frock!”
“D’you like it?” said Mary with a glow of pleasure.
“Like it! It’s lovely! But what chance d’you suppose I’m going to have against that!”
Mary laughed. “Shouldn’t think you need worry!”

- R. C. Sherriff, The Fortnight in September, Chapter 24

This is a novel published in 1931, which describes a fortnight in September in which an English family consisting of Mr. and Mrs. Stevens, Mary, Dick, and Ernie go on a holiday. One one evening, Mary had arranged with her friend Jessica to go for a stroll along the promenade, and Jessica appears and gives compliments to Mary about her frock.

In this part, I wonder what this underlined expression means.
I assume that it might be a response to Jessica's remark, "But what chance d’you suppose I’m going to have against that!", which, I guess, means "By the way, based on what possibility do you think I am going to have a dislike against that pretty frock," (I hope I am going in the right direction. ) but I am still not sure what this underlined sentence means.

 

[Tarheel]

It's hard to say. My best guess is that Mary is paying Jessica a compliment in return. Maybe she's saying that with Jessica's good looks she doesn't need to worry about getting attention.

 

[5jj]

If they are going for a stroll along the promenade, they might expect admiring looks from young men. There might be gentle rivalry between them as to which will get more such glances. Jessica suggests she won't have a chance of winning because Mary's frock is so stunning. Mary's response suggests that Jessica looks very attractive.

 

[5jj]

I encountered the expression "Shouldn’t think you need worry!",

You saw those words. They do not make 'an expression'.

 

[Rover_KE]

Mary laughed. “Shouldn’t think you need worry!”

I expect you're aware that Mary omitted the subject of her sentence — 'I'.

 

[Coffee Break]

@Tarheel, @5jj, and @Rover_KE,

Thank you so much for the explanations!

Oh, so it can be assumed that there is a gentle rivalry between the two girls in terms of attracting boys' attention, and Mary is assuring Jessica that, even though Mary's frock is very pretty and it makes her look very beautiful, Jessica does not have to worry whether she could get enough attention from boys, because she too is very beautiful.

If I understood your explanations correctly, I think I might rephrase those sentences like the following:

“D’you like it?” said Mary with a glow of pleasure.
“Like it! It’s lovely! But what chance d’you suppose I’m going to have against that!” (=How can you ask me whether I like it? It is lovely, obviously! By the way, by what possibility, do you suppose, would I have a remarkable beauty which can be compared to that beautiful frock?)
Mary laughed. “Shouldn’t think you need worry!” (=I shall not think you have to worry about attracting boys' attention; you are already beautiful even without this beautiful frock!)

I sincerely appreciate your help.

 

[Tarheel]

@Coffee Break Wow! That's a lot of analysis.

I think you understand it pretty well.

 

[Barque]

Oh, so it can be assumed that there is a gentle rivalry between the two girls in terms of attracting boys' attention,

There may or may not have been any such rivalry. That conversation could have happened even if they'd never had any such rivalry. Jessica could have just been teasing Mary, saying "That frock's so pretty that you're going to get a lot of attention while I won't get any".

The word "to" has been omitted from before "worry". That works in a structure like this. You don't need come in. I think (I might be wrong) it's more BE than American.

 

[Tarheel]

@Coffee Break Although it's possible, I suppose, that there is not a good-natured rivalry between the two women, it's a fair assumption that there is. As you read further you'll probably be more sure.