Half siblings sharing a room

[kiana2015]

I currently have DD who is 2 months, my partner has a DD who is 6, she is likely to start staying over again for the first time in a while and I'm wondering how to fit everything to ensure she doesn't feel like she's just plonked wherever. Basically we have two bedrooms in our flat and our DD obviously sleeps in our bedroom and even when she's older I don't mind her coming into our room whilst her sister is staying, which would likely be once or twice a month,
the issue I'm having is with DD's cot in her bedroom, there is no room for another bed, the cot does turn into a toddler bed but this would still be too small, I've obviously thought of air bed etc but I don't want her to feel like DD has taken over the entire room and she is left shoved in the corner l. I know I'm asking for the impossible here but has anyone any suggestions beside moving which we are looking into next year

Bunk beds where the lower level could be a cot?

No space at all? Not even one with the storage underneath it like a half-height loft bed so you don’t need other furniture?

My niece and her stepsister shared a room with a loft bed (eldest girl was 10, so a little older) and a low bed at 90° with desk and chest of drawers underneath the high bed. It was cramped but it worked.