Does the contiguous country rule still apply if staying in Canada for over 30 days?

[qwe321]

My mother-in-law is currently in the USA on a B2 visitor visa. Her I-94 expires at the end of April 2018. If she goes to Canada to visit my family for 5 months, are these 5 months counted towards her 6 month stay in the USA as if she's overstaying her visit in the USA? According to the contiguous country rule (https://help.cbp.gov/app/answers/det...-b1-or-b2-visa), a trip to Canada or Mexico from USA while on a B2 visa counts towards the 6 month maximum allowable stay in the USA if the trip to Canada or Mexico is less than 30 days. But what if the trip is over 30 days? Does the time spent in Canada still count toward the 6 month stay if she re-enters? Or does the "clock reset" i.e. she can get a renew her I-94 and get another 6 months? And, what if she's already been in the USA for 10 months so far (through an extension she's obtained)? Would she encounter problems when attempting to re-enter after staying in Canada for 5 months?