Sippy cup?

Our baby is 6 months old, we were told at her 6 month check up to start introducing a sippy cup with water.

Backstory: I want to breastfeed/nurse/pump as long as possible. I have a large supply of frozen milk also. We were also told to stop the bottle no later than 1 year old.

So my question is, can I continue to pump/use frozen milk and give baby breastmilk in a sippy cup once we stop the bottle? Or what do I do when she turns 1 and can't have a bottle anymore? I work so I can't 'boob feed" her but I'd like to continue to give her breastmilk.