Male/Female Integration issues

Question
Dear Norman,

 My friend Jamie and I recently moved in together. I have a 2 year old grey Tabby and she has a 3 1/2 year old long hair Calico mix. Last night we tried to introduce them to each other while holding them in our respective arms and Loki (my Tabby male) was alright and seemed friendly but Princess (Jamie's long haired Calico) began hissing aggressively at him. Before this instance Jamie has told me that Princess is a very benign and extremely sweet cat who has never had issues with any other cats in the past. She (Princess) has lived with two dogs for the past two years with no problems what-so-ever and Loki has also lived with two dogs in the past with no problems as well. We are wondering if there is anything we could possibly do to ease the integration process between the two of them. Please Please Please have answers for us or at least a couple tips to integrate my little boy with Jamie's sweet baby girl.

Answer
Jamie,

What I am about to tell you is very counter intuitive.  I would let them meet each other (now that they already have), and ignore any discussions they may have.  Let them hiss and spit and carry on even loosen up some fur.  This is a normal "getting to know you" ritual and, given their ages, could take a few weeks to a couple of months.  The best thing to do is to leave them alone. Rarely will two cats hurt each other, so, even if they seem to be "fighting", it is mostly noise and little real mayhem. If they begin to play chase, this will be a good thing, even if it ends in a mock fight.

On rare occasions, certain cats (like people) will take a dislike to each other, but I would not worry about that at this point.

Any human interference with their "getting to know each other" rituals will be counter-productive and will tend to draw thew whole ritual out even longer.

Please let me know how it goes.

Best regards.... Norm.