My greys, like Susan's, tend to be a bit breed prejudice. If you are going to introduce, then yes, muzzle - but the other dog should be muzzled too so she is not vulnerable. If she is with much smaller dogs, the muzzle for them is less critical, but she most definitely should have one.
But it's really rare that mine are ever with any other breed - and JJ is highly reactive to other dogs when he is on a leash - less so off leash - and him being attacked by a loose dog made it worse, of course, so we just don't push it.