How do i apply for s1 visa for my mother?

Hi, my mother and i hold a kenyan passport. Is it possible for my mother to apply for her s1 visa immediately when i get my z visa ? Or do i need to wait for a residence permit? also, is it possible for her to come with me on tourist visa and then apply for an s1 visa when in china itself ? The company refused to provide an invitation letter for her but can give in a supporting document saying i work for them and that she is my mother. Please advice.