I am sure there are others more experienced with this situation than I am who will chime in. I have often known of mother cats who at some point decided that their children were no longer welcome. This could, though, just be a very stressful time for Willow, and she's just in a bad mood. How long ago did Popeye have her kittens? I would, for now, just try to find time when you can just focus on Willow, quiet time just being with her and petting her, or just hanging out in the same area with her. It's a big adjustment and disruption to her whole life, and her own daughter's at fault! Give her a nice skritch for me, and just tell her you'll always love her, no matter what.