[bewitched]

I generally just let them get to know one another face to face unless there is more than minor arguing (I've owned lots of cats and only had this problem once). I also agree with younger boy.

I'd also be prepared for some standoffishness from Tango, towards you. And don't be surprised if she has a couple of "accidents" because she's miffed about the new addition.

Really, at worst they will end up ignoring each other...it is much more likely they will be good friends after a couple of weeks.