i think a lot of it's developmental and depends on your kid like so many other things. some kids do it at an earlier age and some later. from what i've read i don't think there's much you can do to speed it up (and a lot of things you can do to stress your kid and yourself out). it'll happen when it happens.
Re: Night time potty training
she is too young to expect her to be able to hold it overnight. Please see this article:
https://tinyurl.com/2cpdog3