sandals
there have been comments already about the baby sharing her room if they don't manage to move house in time, and her helping to look after the baby if they need a break
they haven't implied that its forced babysitting, nor have they implied its going to be more than a few hours. Also, she can say no, cant she? she doesn't even live there! she wont be there to have a baby left with her!!
Sharing a newborn/small baby's room (any age until reliably sleeping through and not having feeds) - inappropriate
many children share rooms with small not reliably sleeping through children FULL TIME. Is that inappropriate too? thought not.
The parents to be have chosen that slepp deprivation for themselves, they have absolutely no right to inflict it on anyone else. Ops DD should not be having to deal with, settle a baby at night, which is extremely likely if they're in the sane room as her. That is the parents job
by that thought process, you should only have 1 child, shouldn't you?
nobody has suggested that the dd would be settling any babies at night, you've just totally made that up!