19 month old will only take milk in a bottle

[knat]

My 19 month old dd will have juice in a cup with a lid no spout really well but will only take her milk in a bottle. She has milk in the morning on waking and at bedtime. I don't mind the bedtime one being a bottle but this week I tried her morning milk in the same style cup as her juice. The first morning she took a couple of sips and then left it and ever since (for a week) she won't touch it. My initial thought was that she didn't really need it otherwise she would drink it anyway. (She gets a lot of calcium from other dairy products and has approx 8 or 9 oz in an evening). Her solid intake and juice intake didn't really increase at this time to compensate for the lack of milk first thing. However I don't know if it's just coincidence but since missing her morning milk her sleep pattern (day and night) has changed and is shorter in both instances. I've reverted back to the bottle this morning and she drank all 7 oz without stopping! Any ideas?