My daughter will be 11 months on Sunday. I introduced a sippy cup to her for the last 3 months just with water. All last week I've been giving her formula and the cup because I'm sick and tired of cleaning bottles. She would drink about an ounce and a half then cry for her bottle. But, today she did she went all day using the sippy cup instead of her bottle. Is it too early to just use a sippy cup and get rid of the bottles completely?