I wouldn't use any vitamins in her water, you wouldn't want anything like that to get in her eyes, for example.
It's better to buy the separate supplements, at least a PLAIN calcium (no vitamins at all, just calcium mineral) and then a multivitamin powder. You already have the calcium with D3, so you can use that about twice a month.
The PLAIN calcium is the supplement you can use at every feeding, but the other two are best is used more sparingly (about twice a month, each.)