No, they didn't forget who she is, don't worry. If anything, they're shocked that you took off their friend, and brought home this complete stranger! Imagine it...she's come home smelling not only like herself, but a MYRIAD of other cats (and perhaps even a bit of dog), so they're pretty confused (despite the fact that she LOOKS like herself), and they think she's not who she APPEARS to be. Does that make sense? They rely much more on scent than on sight, so to them she's not herself. Give her about three or four days of solitude, and opportunity to bathe herself and get her own scent back, and get the three back together. The other two will be a bit suspicious at first, but as soon as they smell HER again, instead of the other cat you brought in, they'll be right back to normal, if not completely happy to see their friend again.
Our Sunny does the same thing to her brother (blood-sibling) Hobbes. When we've had to take him in to the vet, she is just ANGRY when we bring him home. She mopes around the house, missing him, and hisses at him every time he comes around. This continues for about two or three days, and then things are ok again, and she's ecstatic to see him again.
No worries...she just has to smell like her again.
Oh, P.S. Not to mention...she might have a slightly different scent now that she's spayed. They'll be fine, though, in the long run. I promise!