will my mother lose her tourist visa

Your mother will not automatically lose her tourist visa, because you file an immigrant visa peition on her behalf. However, once the immigrant visa petition is filed, your mother is likely to be denied admission. CBP will deny admission because your mother will be viewed to have immigrant intent. It is not advisable for your mother to attempt to enter the country with a tourist visa while the immigrant visa process is pending. Your mother risks not only being denied admission, but expedited removal. You can read more about family immigration at http://myattorneyusa.com/family-immigration.