On Tuesday, we let them in to our bedroom. And then put them back in the bathroom. And then let them in the bedroom. We temporarily barricarded the bannister, but had nothing to block the stairs, so we couldn't let them free range.
We made sure Izzy started to become aware of them. She'd been aware of them since Monday, and wasn't happy. On Tuesday evening, I took her in to the bedroom, while Shelby and Lewis were playing. I sat on the bed with Izzy, stroking her and talking to her. She was Not A Happy Cat. She tried to hiss, she made that "intruder" yowl, which I tried to cover up. After a few minutes, I took her out.
I repeated the exercise later. More hissing and growling, but the kittens seemed oblivious. Later, when the kittens were back in the bathroom, I took Izzy upstairs. She refused to stay.
She ignored me for the rest of the evening, and was a bit more cuddly with her Dad. She also refused to come in to the bedroom that night (she normally comes in when we are safely in bed). And she refused to stay when we brought her in the following morning.
We got some cardboard out of the loft, and fashioned a barrier for the bannister, which folded round to block the top of the stairs. With all the other doors shut, we were able to let the kittens free range between the bathroom and our bedroom.
Later in the day, I cleared the stairs and hall, and now their free ranging area included the stairs and hallway. It's a bit of a challenge when we need to answer the door.
Izzy is not happy. No surprise. Despite lots of cuddles and reassurance, she is busy being Not Happy. She went out into the garden, and tried to climb on the (collapsed) swing bench. Sunshine, our friendly little Leghorn, watched her with interest. Izzy interpreted the interest as a bit of a threat, but was unable to escape.
Sunshine decided to go and say hello. She climbed up the broken bit of swing to get closer to Izzy. Unfortunately, it was an awkward climb, ad she had to flap her wings to help her balance. Izzy tok that as an attack and ran off. She's back in the house now, and is lying on one of her (many) beds on the sofa. I picked her up for a cuddle, and she purred for a while... then she remembered she was cross with me, and leapt off me.
We did a couple more "take Izzy into the bedroom to watch the kittens" things, and then our overseas visitors arrived.