Extended Visitor Stay Question

Hi, my friend has recently traveled to Montreal, she initially entered as tourist since she took a semester off university to visit the Canadian provinces, she has been here for 2 months and she told me she wants to start studying English, however I´ve been checking for her and I have a few questions I hope someone can help me solving this...Unfortunately she cannot apply to a Canadian University since her English skills are not good enough.
Can she apply for an extended stay in Canada? What are the chances of this usually being rejected?
Would she be able at the same time to apply for a student permit within Canada/Quebec even if she only plans to stay for another 6 months or does she need to go back to Mexico and apply from there?
Would there be any problem with the CAQ by applying for an extended stay?
Also, can she sign a 1 year lease in an apartment for her remaining 4 months and later sublet it? Is that illegal?
One more thing...
She has a canadian citizen uncle living here who´s retired and receives government pensions, would the pension be an issue to sponsor her as a permanent resident? How long does this usually take? and can she apply now, while she is in Canada based on the description I provided above. Because if she has the chance to become a permanent resident in Canada, then she will consider coming to finish her university studies in Quebec.
Thanks for your time.