This might be worth you reading
http://www.sacn.gov.uk/pdfs/final_sacn_stateme nt_on_good_night_milks.pdf
at 7 months it's alotto expect a baby to sleep through, in fact at 17 months I think it would be a surprise unless they've been trained into, which obviously has negative consequences on their development.
Just like other stages in their life they will do it when ready, they walk when their legs are mature enough to support so, they will sleep through when their brain has developed enough to self settle alone. Until then it's your job to help comfort and settle them without stress.
Personally I cannot stand the idea of goodnight milks, it's not going to do their digestive system any good whatsoever and I wouldn't do anything detrimental to a child's health for uninterrupted sleep. If breastfeeding replacing the vital evening feed with another milk is going to really affect supply.
Watering down bottles is also undesirable, Hyponatremia can result from doing this too much.
If you personally have a problem with your baby's sleep pattern then perhaps the books by Elizabeth Pantley are worth a look for kind suggestions.
But to me, as a mum of 3, she sounds totally normal to me.
Sleeping through is not some holy grail that a mum should judge her worth by, make the most of those lovely night time cuddles...they soon grow up!