Was she the one that travelled to Canada 2 months ago... If so and she did not overstay why doesn't she try for a multiple entry visa as she has family in the country. She can say that she has friends and family in the country which is true. If she has never travel to canada it may be better applying for a single entry visa stating she has family and friends here and wants to visit.
I BELIEVE it is better if the letter comes from her family member so her cousin. Yes she would be able to visit you at anytime even if her cousin gave her the letter.
A letter from her job will help her when applying for the visa. As per the lenght of stay, she has 6 months in the country when she enters. From what I have seen on the forum a lot of people will get the visa and have a flight booked for 2 weeks after the arrival then once they land and are in the country change the flight date. By showing an immigration officer that she has a job letter, flight book, family in the country and not saying she is in a realtionship with a canadian this increases her chances of being able to come into the country.
Remember that a visa does not give you access into the country, it only gives you the opportunity to book and flight and leave the country of origin on that flight... There is no guarantee the officer will let her into Canada but her chances are increased if they see she has no ties.
I hope this clarifies any questions you may have you can send me a personal message if you have other questions and I can tell you more about my personal experience with my husband. Btw from your first message I see the birth dates and you and your partner are the same age as me and my hsuband
