So she applied for PR. Now tell, do you live with your girlfriend as a couple and have you been together more than 12 months? If this is the case, she should have included you already on her application. If that is true, she needs to notify the visa office immediately and ask to add you to her application as a common law and you will get a PR visa too. If she doesn't do that and lands as a single and they find out later that you lived together and she should have included you, then she has a big problem.
If you didn't live together, no problem.
As for getting married, problem is, if she got her PR visa as a single, she can not land as a single if she just got married. This is very serious business. Getting married before landing and then landing on the visa she got as a single as seen as misrepresentation, a lie to immigration and they can revoke her PR again if she does that. Even if they let her keep her PR, she can never sponsor you so don't do that.
You have two options. You can get married now, tell the visa office that she got married and ask to add you to her application. She will have to return her visa to the visa office if she got it already because it is now invalid and they will issue her a new visa and you get a visa too when they complete your processing. Second option, you don't get married now, she lands as a single, then comes back to you to get married, then goes back to Canada and applies to sponsor you.