Agree with PP - we live in a very tropical climate and I introduced a sippy cup when we started solids at 6 months. I basically let my LO self-regulate how much water she wanted, but just kept in mind the recommended daily maximum, which I think from memory was around 120mls. She never wanted to exceed that. She was on five BFs per day though. The concern with giving water to babies is mainly for babies under six months old, when it can lead to water intoxication. If your LO's pee is dark yellow and she's getting constipated, it does sound to me like she's a little dehydrated so I would either offer more frequent BFs or more water. xx