I am not going to give my coworker water when she asks for it.
Why would you deny her?
Doing that will make her weaker and I hope that it will cause her to dedicate more time on her job
It is ok to refuse to do something others can do for themselves. You should not have to be a water boy if someone is capable.
I tried to be nice but I can't stand her. She's annoying and she never quits.
I am sorry about that, ask her to get her own water.