there must be something with cats that have calico in them that makes them all act the same (well, most of them). i have a calico mix (stormy) and she doesnt really like my kitten Mittens. she will hiss at mittens all the time and mittens will try an trip stormy. stormy has calmed down a lot since i got mittens. Stormy never hissed at Smokey (unless he was trying to do "stuff" to her that she didnt want, and they are brother and sister). Smokey and Stormy have been there for each other since day 1.
give your furrbabies some time. its harder for your calico in some ways to cope with the new kitty in the house because she is so old (not to be mean) and it sounds like she doesn't want the "little twerp" to take over her home.