Can 「〜たら〜た。」structure mean "If I had~then I would have~"?

Question

This is probably a basic question on tense / aspect in conditional sentences but I can't find an explanation and it would be very useful to resolve.

I will illustrate my question with an example from a drama I saw yesterday.

Context:
A young woman has been reunited with her family. After suffering for a long time, isolated from her family in Hokkaido, she had heard her successful sister on the radio. She then fled to Tokyo, initially not to find her family but by chance they are reunited. She relates to them how she heard her sister on the radio and asked herself, how could my sister be so successful and I turn out like this?. She then says:

「お姉やんに会ったら、もっと惨めな気持ちになった・・・(うらやましくて、うらやましく・）」

Does this/can this mean:

"If I met you, my older sister, I would have felt more miserable. (I was so jealous. [That's why I did not look for you])."?

Or, does it/can it also mean:

"When I met you, my older sister, I felt more miserable. (I was so jealous)."?

I think it is the first*, or based on the context I describe (I don't think I missed anything), it could be either.

If I wanted to make the first statement then I might have used the present plain form in a longer sentence：

「お姉やんに会ったら、もっと惨めな気持ちになると思ったから会うつもりはなかったんだ。・・」

But that is because I am a weak speaker and try to minimize the chance of being misunderstood.

*If she had said ~なっただろう the question might not have occurred to me.

Answer 1

My answer is based on the assumption that the sentence in question has been correctly transcribed.

「お[姉]{ねえ}やんに[会]{あ}ったら、もっと[惨]{みじ}めな[気持]{きも}ちになった。」

can only mean one thing with or without any further context. It means:

"When I met you, my older sister, I felt more miserable." to borrow your own TL.

A native speaker would never say 「お姉やんに会ったら、もっと惨めな気持ちになった。」 if she has not met her older sister as she speaks this line. 　「もっと惨めな気持ちになった」 is a simple statement of a fact. It is not like the English "I would have felt more miserable.", which only expresses conjecture.

There are different ways to change the Japanese sentence in question into the equivalents of the English sentence "If I had met you, my older sister, I would have felt more miserable." I am going to start with the least formal and work my way up.

1) 「お姉やんに会ったら、もっと惨めな気持ちになったと思う。」

This is the easiest and most informal (or almost too informal); therefore, it borders on "being sloppy". You could end up sounding uneducated, too. Not recommended by me but you will hear this format once in a while.

2) 「もしお姉やんに会って（い）たら、もっと惨めな気持ちになって（い）たと思う。」」

There is a pretty big gap between #1 and #2 in terms of clarity and the listener's impression of the speaker. This structure, you will hear very often.

3) 「もしお姉やんに会っていたら、もっと惨めな気持ちになっていただろう（or いたであろう。」

4) 「もしもお姉やんに会っていたとしたら、もっと惨めな気持ちになっていたことでしょう。」

3) is the structure you will hear a lot in English classes in Japan as the translation of the English "I would have ~~~ if I had ~~." In real life, it would sound almost stiff. Replace 「であろう」 with 「と思います」 and you will basically have the most realistically polite way of saying this.

4) will make you sound like an upper-middle-class dame. It sounds very nice but to use it naturally, all the other things you say will need to be just as refined.

I personally recommend 2) and 3).