Now that your girlfriend has been called for an interview it is likely she has reached the point considered 'removal ready' so it is too late at this point to submit an in Canada spousal application even if you were married.
If you genuinely are in a relationship and want to marry by all means go for it. Being married though does not stop deportation from proceeding.
Your girlfiend will likely be offered PRRA - and can take that which will be a number of months until a decision is made. You could marry during that time and submit an out of Canada application through her own country. Some of the waiting time she will be in Canada for PRRA, but the percentage of positive PRRA decisions is overall about 3 of 100 so she will likely have to go home once the decision is made.
If that is the case she should buy her own ticket so removal costs of $1500.00 don't have to be repaid if the PR application from outside Canada is successful. She will need to be approved for ARC to overcome the deportation order.
You need to expect a period of separation unless you will go with her to her country to wait for the answer to the application or reside with her in her country if she is rejected.
Many, many times these applications work out in this situation, but be completely cooperative with CBSA, get a travel document if needed ready to go. ARC approval usually involves contacting CBSA to ask if there is a concern about return of a person to Canada following deporation. Imagine how much easier the answer yes comes when a file is reviewed seeing full cooperation and no glaringingly awful immigration history beyond refusal of a refugee decision.
Good luck. I hope the relationship is genuine. You will need to prove that, especially in the circumstances so use the time wisely over the next few months and really think about what next steps are best in both your circumstances.