回複：簽證到期前想再次來美, 怎麽回答為啥又來了?

Normally, a visistor is allowed to stay for half year annualy. If your mother leaves US before B2 type I-94 expires and come back next day as B2 visitor, it does not make sense as a temporary visitor

In principle there is no minimum amount of time you mother is required to be away before returning to the US but if she turns around much too quickly she may be questioned or even refused admittance at the POE.

If she just returns to China and has a valid reason to return to the US she needs to be prepared to prove it to the officer upon arrival in the US. However, if she were considering using her tourist visa to leave and come back as a means to reside in the US part-time and legally, then at some point it may backfire.