How do you use "it was" for decisions (and do you put a comma before it?)

Hi, English is my second language and I'm trying to write a paragraph that goes something like this:

"She wondered whether to feel fond or irritated, when he continued, 'she's my friend. I'll help her.'

Fond, it was."

I feel like that last sentence is weird for some reason. I've heard people say "it is" in speech when making a decision between two things (like "hmm, do I use the plastic cup or the glass one?" sound of glass breaking in the distance "plastic, it is"), but the way I used it feels kind of awkward, like it's Yoda trying to say "It was fond" or something. Is it because I used the past tense? Is it ok to make a sentence like that in writing?

And even if it is correct, should that comma be there or should it be "Fond it was"?