As a permanent resident of Canada, you can certainly play a supportive role in your friend’s desire to visit Canada. While you cannot directly sponsor your friend for a visitor visa, you can assist in other ways. For instance, you can provide a letter of invitation that she can submit with her visitor visa application. This letter would outline your relationship, the purpose of the visit, and details such as the length of stay and where she will be staying.
Regarding marriage, if you and your friend decide to get married and you wish to sponsor her for permanent residence, you would need to be at least 18 years old and meet the necessary sponsorship requirements. The marriage must be legal in the country where it took place as well as in Canada.
Once married, you could sponsor your spouse under the Family Class sponsorship. This process involves proving the genuineness of your relationship and meeting financial requirements to ensure you can support your spouse when they come to Canada.
Keep in mind that marriage should not be entered into solely for immigration purposes, as this is considered fraudulent and can have serious legal consequences.