If your job is full time (contractor or permanent, does not matter) and its NOC 0, A or B category job then you can apply for your spouse's OWP. You need your offer letter (with job responsibilities defined and stating that you are full time), couple of salary slips, and your work permit to apply for OWP of your spouse.
As it is a new work permit application and not an extension of your spouse's current BOWP so you can apply anytime but apply it ASAP as her permit is expiring in April. I am not sure if in this case she will be considered on implied status once her permit expires in April.
EDIT: she will be considered on implied status but I am not sure if she can work in this case.
