My partner is canadian, Im Dominican, I got a canadian visa first time for 6 months because they dont give visas with expiration date longer than the one in your passport, so after 6 months when my passport and visa expired, I got a new passport and applyed againg and I got 6 years visa, so my sugestion before her apply for the visa to check if is ok the next points.
1.- Is important that she has a permanent job.
2.- bank account, credit card. etc.
3.- If she traveled before to some other countries for vacation.
4.- How long have you been in relationship
5.- How many time in a year you visit her.
6.- Give them a lot prove that you are un real relationship.
7.- You must convince them that she will be back.
8.- Invitation letter telling them why you want she visit canada, try to make a very good one invitation letter and clear on everything you says.
In the process of the visa when you apply they dont make any interview so you just deposit all the papers and go back to pick up your passport after 7 days and there you know if you get or not the visa, so is very important that you or she provide as much information and papers possible to prove them that you are in a real relationship and she is not planning to stay living in Canada.
If she get the visa that doesnt mean she could enter to Canada, maybe when she arrive to Canada they will send her to inmigration department and there an inmigration agent will make random cuestions to make sure all the information that they have is real.
If you are applying for one enter visa the cost is 75.00 American Dollares, if is Multiple visa the cost is 175.00 American Dollars, the forms are in the webpage of the Canadian embassy and is easy to download and also give you all the information you need.
Is sad for me to say this as Dominican but is the truth, when is something with Dominicans the first thing will come to their minds is that once she arrive to Canada she wont go back to Dominican and she is trying to use you, so is important that you prove they are thinking wrong.
Good Luck!!!!!