Your daughter could have transitioned over a year and a half ago to a regular cup. No, it's not going to interupt anything by transitioning.
Sippy cups were originally intended for travel only, but many parents out there used them for every day out of, well, laziness. Now all new moms think they're suppose to use sippy cups. Nope. Right when a baby can tilt and hold their own bottle you could have introduced a cup with drain holes, like the throw away cups they have now. (companies got rid of traditional transition cups with rounded bottoms when they started making money on sippy cups)
Get some throw away cups with drain holes on the spout. You don't want anything that they have to suck on or it's just like having a bottle. Start with the first drink of the day and stop using sippies all together, except for travel. All meals and snacks should be at the table so there's no need for sippies at all. Once you feel she's doing fine with a draining cup then take the top off and get her used to using it that way. Be sure it's when you're sitting with her for snack or meals and any spills that she makes have her help you with clean up to learn responsibility.
My two older sons were using transition cups well before their 1st birthday. My 2nd was regularly using a transition cup at 6 months old. By their 1st birthday they were using open cups. My triplets took longer because they were 2 months premature and took longer to learn fine motor skills.
Bottles are only a tool to feed baby. Once they can hold and tilt, it's time for a cup.
K. B
mom to 5 including triplets