can you keep them and let frazzle just get use to new cats coming and going?

i have a cat here that i accually just adopted..named TURTLE of course i switched her name to MYRTLE..

but long story short...i was told she gets along w/other cats.
She hates other cats.GREAT!

but...i find that as time goes by...she kind of goes off to her own little area(lots of different areas)and she seems pretty happy.
she swipes and growls(accually clucks at my cats like when they look at birds out the window).
i keep thinking she wants to eat my cats because of her clucking sounds.
but all in all...Mike talked me into keeping her...and so far no injurys and noone seems scared of her...they just know to not go to near her.

i'm not happy about the whole thing but...everyone seems happy.including mike.
she sleeps on his chest...