I wanna sign in from my phone only

You should never share an Apple ID, they are not meant to be used by multiple people. There are other ways to share data and apps in a controlled manner by using Apple Family Sharing. If you don't want her to have access to it, I would suggest changing your password and not telling her what your password is then she will have to use a different ID. Otherwise you could create a new one and use it just for you

Okay, just sign in on your iPhone, don't sign in or set up an email account on your computer.