If you gave Val permission to bimbo others with your supervision, then all you have to do is have Val in Bimbo Personality, and no one else who Val can bimbo currently in Bimbo personality (so if your problem is that Julia's still in Bimbo personality, change her back), and go find a screen around the town that isn't the bedroom where a Portrait appears in the top left. Each person she can Bimbo is bimbo'd on a different screen, by clicking the Portrait. Molly is bimbo'd in the store, Kate on the streets (even if you've never met her before), Sarah via having her as not a slave talking to her in the School Hallway and then going to your bedroom and clicking her icon there (the reason why she needs to not be a slave. Being a slave overrides her bedroom icon for the bimboing with her slave talk dialogue), Cassandra in the school Hallway, Brittany in the Enchantment shop she runs, Dr. Tiff in her classroom/office, Ashley in your living room after you've cured her, and so on (go whereever you expect them to be that isn't your bedroom, for all the non-Sarah ones)
Once you've gotten to the point where Val can bimbofy up to one other character at a time at your discretion as described before, then each character that can be bimbo'd at your discretion will show up whereever it is they show up, so long as there is no one currently in bimbo state due to Val. Kate shows up in the streets just outside of your house (the screen where you can transition to either your living room, the item store, the bounty store ran by Eric and Erin, the screen of the area just outside of the school, or the screen of the area just outside of the Enchantment shop). Once you click on her portrait there, and agree to let Val bimbo her, she should show up in your bedroom right away, and only go back to her spot on the street if you unbimbo her.
Sarah needs to have been dollified (meaning you've turned her into a doll through the Stone Skin spell (evidenced by the presence of doll joints on her arms in her portrait)), and must also *not* be a slave. At that point, after getting to the "you can have Val bimbo one person at a time" state of Bimbos Gone Wild, you'll see Sarah's icon in the school hallway, and then after talking to her there, you can find her in your bedroom so long as she remains not your slave, where you can bimbo her (the only case where Doll Sarah's portrait will change at all from personality alterations, as no other personality has an alternate version for Doll Sarah).