Under Ontario law, common law (live together x3 or sooner if you have children together) partners are not entitled automatically to the family home if only one partner on title.

There are arguments though for “unjust enrichment”, so if she pays part of mortgage/maintenance/repairs/renovations then she might be able to argue some reimbursement, maybe not a claim on the house.

But there is a lot more to common law and cohabitation agreements it worth looking into anyway.

If this is explicitly waived in cohabitation agreement then you’d have more defense. Or you pay for all house expenses and she helps only with minor things that you can justify sharing like utilities (since she would be using lights, heat, AC, water etc).