I would say this is normal behavior for all cats in general. A friend of mine has 3 domestics (2 female and 1 male) and a couple weeks ago we found a 1 year old female outside crying in the corner of his apartment building and shivering from being so cold... brought her in and immediately his male started acting exactly the way your saying your female is.
I wouldn't say the cats were mad at their owners, just that cats are territorial by nature... so any new animals on their turf will be met with hostility. I wouldn't let it bother you in all honesty, as it's not being directed towards you on purpose... she is just pissed off that some unknown cat is is around. Introductions of new cats are process and will take time to get them use to each other.
I watched this multi-part video on youtube that seemed really informative with regards to introductions:
http://www.youtube.com/watch?v=H_mgXHAMDZI