Even thou i applt for her supervisa?PLEASE DO NOT give wrong info if you don't know how a certain application works. Blank stamp with no date means it expires in 6 months, so YES, you would need to apply for an extension if you would like to stay beyond that period. At least this is what CIC says here, http://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=209&top=17