Dear Devpratap ...
Lets say for a minute that your wife somehow manages to get the Visa ... then what?
If she herself knows that even 5.5 score band is not possible then is there any point enrolling in a classroom where English is the medium of instruction and unlike India or any other country they can only explain in English and no second language ... probably French which again is not feasible.
Please understand that its a tuff and very competitive world out there.
Just getting visa , odd cash jobs , somehow getting a PR are all so difficult.
So in this situation I would highly recommend you to enroll your wife in a good English institute for example British Council in a 3 to 6 months advance course and you will see the difference..... by the end of course she would feel confident enough to score even 7 bands score.
2nd option is to enroll her for ELICOS course in Canada but that would be 10 times more expensive and visa could be an issue.