moving bad sleeper dd2 in with good sleepr dd1?

[bagpussmice]

dd2 is/always has been a terrible sleeper - she is now 16 months old, have tried everything - cc, in bed with me, all sorts... doesn't seem to make any difference. She can settle herself and does on several occasions in the night, however, once a night she wakes up and screams the place down until she either gets more milk or comfort...
I have heard children sleeping better when in a room with brother or sister... and wondered whether moving dd2 in with dd1 (she is 3.5 and a very good sleeper) may settle/reassure her in the night - anyone else tried this?
Any comments or suggestions would be warmly received!