my sister every morning come to my house

Hmm. I dont find any problem in the face of the situation. But your question is not so clear. Has it become a problem for you, i mean your mom looking after your sis' baby, and how? Are you also working? Or, is your sister giving you somekind of trouble or are you losing your privacy or something. Then the situation changes and you have to think about it. Just for argument's sake, if you feel like, i am just curious to know your answers. Good luck and take care.