I was also given similar advice so as not to encourage them to wake and want a bottle at night, similar to a previous poster, it forms a pattern.
However,I was given this advice at 8mth, and so I think 6.5 mths still a bit young and yes I would give a bottle. Well, that was worked for us, a bottle would get her back to sleep.
But you could try offering water first?
I think this advice makes sense, but more when the baby is eating 3 decent meals a day and food should take up most of thier nutritional requirements, around 10 / 11 mths in my case.
DD is now 14 mths and when she wakes in the night, doesnt really want either water or milk, so something else causes her to wake.