Okay, why are we all getting excited here and losing sight of the main point? We seem to be descending into drama about whether the OP was "right" to feel what she did, or how she's being hypocritical. But I believe the post was made because the OP wanted to understand why the ISTP felt what she did, because she had been left with the impression that she was being judgmental and dismissive. She felt that the ISTP was judging this woman negatively as a human being, rather than negatively due to her actions, because emotional language was used. Fi users often make this mistake.
The kind of posts I've been seeing most recently seem likely to make the OP feel more confident in their negative opinion of Fe, due to her being condemned for her feelings on this matter. I consider this unfortunate, because she seemed to actually want to understand why the other woman acted the way she did. Many Fi users hold negative opinions of Fe, and never even give us a chance to explain our side of it.
So, OP, I want to try and explain what's going on here. People are angry with you because they feel that you are devaluing the ISTP's attempt to help, and calling her lacking in compassion, simply because it wasn't done the way you would have done it. They are not understanding that you are actually most annoyed because of your perception that the ISTP was condemning not her actions, but the woman as a human being.
I tried to explain in an earlier post that you may not have seen, that I believe the ISTP was merely using emotionally judgmental language in order to create sympathy for herself (and for the children's situation) and draw attention to what was going on, as she has found that emotional appeals and judgments tend to be more effective in getting attention and sympathy from most people than intellectual ones.
In other words, I don't think that the ISTP intended to come across as devaluing the ISFP as a human being, but only to express her frustration and get sympathy. She may have sounded like she was condemning the person, but that's because we tend to identify the emotions with the ACTION, so what we really mean is that the actions appear uncaring, not that the person does. We don't know what the person is feeling, but the point being made seemed to be that the ISFP is performing poorly in her role as a mother, not that she's a bad person. Fi users tend to identify the emotion with the PERSON, so when we condemn the action as uncaring, it's assumed that we're condemning the person as uncaring, when that's not the case at all. We just want the person to start acting like how we believe that someone who cares should act.
Does that make sense?