common law relationship, debts

I am currently living common law with a girl for 10 years now, and things are not working out. She is thinking of leaving me. She owes money to student loans and also has credit cards in her name which she owes money on. If she leaves me, do I have to pay 1/2 of what she owes or liable for any off that

Normally you would not be liable for debts in her name. But she can try to get an order showing that you both indeed treated and agreed the debt as joint debt. It will be a bit hard for her to do but not impossible if evidence exists that that is the case.