We have a big girl on our hands. We gave up sippy cups a few months ago and have been fairly successful in drinking out of a cup. We used to put her back in a sippy if she spilled, blew bubbles, or put food in her cup, and we were doing that regularly but then she figured out she'd rather have a big girl cup like her brother. We haven't had to use a sippy in a few weeks due to spillage.
We also have started transitioning her into her new room with a big girl bed. I might have to break down and buy her girlie sheets and comforter rather than make her use Mason's

hand me down space ones. She doesn't seem to mind, but she does favor girl colors over blue. We tried last week and she failed miserably so we put her in the twin bed last night and she was happy for a bit. She then started coming to the door, we baby gate her into the new room, and we told her if she came to the door one more time she would have to go into the pack and play we set up in her room. She failed and ended up in the pack and play, but she is currently upstairs taking a nap in her big girl twin bed and she hasn't came to the door. She isn't that big to begin with, but looks so small and dainty in her big girl bed.
We also put big girl undies on today per her request. Poor Mason couldn't go 15 min without having to relieve himself where Ellery can go 1 hour plus b

efore she gets the urge. We filled up on fluids and popcorn today and she is proud as she can be to be in underwear. We only had one accident and that was when we were outside playing and she did #2 in her pants as well as #1, but she came and told me asap because she didn't like the feeling. Mason tried telling her it was ok to poop on the potty, he stated "you just have to push a little harder". He also told her not to be scared. I still think she is a little young, but she is expressing the interest so I am not going to tell her no.
Thank goodness I have another child on the way. It is tears of happiness that she is growing up, but I don't know if you can ever prepare for it emotionally.