Thanks for all your reply, but "Canadian women & Baloo" I want her to apply just after marriage because i think if she applies before marriage the high chances are to get declined because she is single and young.
If she applies now, then she has a chance (I understand that it may be small, but it is a chance) that she will be granted a TRV.
However, if she applies after getting married it is extremely unlikely that she will be granted a TRV, the presumption is that she would overstay.
Visitors have to visit, not stay.
Do not expect success if she applies after the marriage.