Whenever I introduce a new cat to my cat, she's extremely aggitated just seeing her even from a distance and she starts hissing and growling. This behavior is consistent whether it's a cat or a kitten. Over the last 7 years, she has never got along with any cat and lives a solitary life. However, she seems to be perfectly fine in front of a mirror. This confuses me.

All the articles I've read says that cats see another cat in the mirror and aren't aware that it's themselves. If that's the case, why isn't my cat aggressive towards her own reflection? What's really going on here?