What does "Her heart isn't in it" mean here?

[on the way]

In episode 2 of Silk,a British Tv series ,Clive,a barrister,is talking to his client,a victim (or maybe just a complaint) in a rape case. The following is a part of their conversation with Clive as the speaker of both sentences.

-But if I had to choose anyone to cross examine you, it would be Martha Costello.
..........
-I know Martha(the defendant's brief) well enough to be clear about one thing, she won't go for you. Her heart isn't in it

I know "go for" means something like "attck",but what does Clive mean with "Her heart isn't in it"?What's the meaning of this sentence?
Any help will be much appreciated.
The time frame is "12:27 " in case someone would ask.;-)

 

[allenman]

Without hearing the actual exchange it's hard to pin down what the context is. Something sounds funny here -- like it should have been "she won't go for it" instead of "she won't go for you".

Regardless, "won't go for" does not mean attack and rarely if ever. It means she won't be convinced to believe you or your idea.

"Her heart isn't in it" means she is not emotionally connected at this time and can not connect with the person or idea regardless of their intent.

We often say this when someone is mourning (after a death) -- for example, her husband just died and another man wants to go to dinner with her. Her heart is not in it -- she's emotionally not ready to think about dating.

Not a teacher

 

[5jj]

This is my suggestion:

She won't go for you - she will not attack you, question you aggressively.
He heart isn't in it -She does not have a strong commitment to, belief in, this sort of approach.

 

[JMurray]

I know Martha(the defendant's brief) well enough to be clear about one thing, she won't go for you. Her heart isn't in it.

As allenman says, it's quite difficult to sort this out without more context, but I'd like to offer a slightly different interpretation.

Perhaps Clive is saying to the victim that he would prefer her to be cross-examined by Martha as he knew Martha would not strongly attack the victim's story (would not go for her) because she would be too sympathetic to the victim's situation to be aggressive (her heart isn't in it).
Perhaps he knows something about Martha's life that makes him feel she would be softer on the victim than one of the other people on the defendant's side.

not a teacher

you're too quick for me 5jj

 

[allenman]

I thought I'd poke my head in here and see if there was a follow-up. What was interesting was to see how my British counterparts (sorry JMurray ) interpreted "won't go for you" entirely different than I did!

It certainly sounds funny in AmE to use it in the context explained.

I'm learning a lot more than I expected on here!!

 

[5jj]

I'm learning a lot more than I expected on here!!

Most of us do on UsingEnglish.