The Government Pension Offset covers situation if a person is eligible government pension and Social Security benefits at the same time - so that is not your situation.
The US-Canada tax treaty covers situations ability of benefits - and not eligibility .
The US-Canada Social Security agreement provides - see above - that if the person doesn't have enough work credit to qualify security benefits - Canadian credits may be taking in consideration - that is exact your situation - because your wife doesn't have 40 US credits - she may add Canadian credits and would be qualify social security on her own record.
She may however apply benefits based on your record - and in this case you need to decide which way is more beneficial.
However if she is eligible CPP/ QPP benefits - she would be exactly under the Windfall Elimination Provision. - Please see the US-Canada Social Security agreement Part V -- A CPP/QPP pension may affect your U.S. benefit
If you qualify Security benefits from the United States based only on U.S. credits and a CPP/QPP benefit from Canada, the amount of your U.S. benefit will be reduced. This is a result of a provision in U.S. law which can affect the way your benefit is figured if you also receive a pension based on work that was not covered by U.S. Social Security. Receipt of a Canadian Old-Age Security pension, which is based on residence in Canada, will not affect the way your benefit is figured. information, call our toll-free number, 1-800-772-1213, and ask publication, Windfall Elimination Provision.
There are probably lots of people who receive foreign pensions (equivalent of US SS benefits) and do not inform Social Security Administration to avoid the affect of the Windfall Elimination Provision.
However - because of the US-Canada Social Security agreement - I believe that SSA might exchange the information with Canada.