Hi!
Congratulations on your engagement! I would state that she is your fiancee, but I would not disclose the date of your marriage or any additional details. Just make clear that your intention is to marry her and you're aware that you'll have to go through the sponsorship process in the future.
Don't forget to include proof that she will be going back after two weeks, enrollment in an university or a letter from work, and proof of being financially able to visit for 2 weeks.
When I applied for my Multiple Entry Visa, my now husband wrote a letter saying that his intention was to marry me in the future and sponsor me so I can be with him in Canada. I was working at that time and gave proof of it too. I got the visa with no problems

I figured they like to hear the truth and that you don't intend to bring her and make her stay illegally (you know the rules), and that she has the financial support so she won't need to work illegally.
Good luck!