This is an indication that the speaker feels the one using 'she' is being disrespectful. Instead that person should have said 'Your mother' or 'Auntie Edna' or whatever else would have fitted the situation rather than just the bald word 'she'. In other words, the comparison with 'the cat's mother' is simply bad manners.
One might call a cat or its mother 'she' but one shouldn't call one's elders and betters by that dismissive name...that was the point I was trying to make above!