I applaud you for trying to be helpful! Both of my son-in-laws married my girls with student loans...great men in my opinion. Maybe you could try and understand your "fear" of debt? I mean really, it IS the way it is, in this day and age. You're going to buy a house and have a mortgage...well that will be substantial debt too. At some point, if things go well for you, you can refinance that mortgage to include the student debt, at a lower interest rate.
One more thing...if you think college is expensive, just wait until you have children...lol ...they cost a fortune, but like an education, are SO WORTH IT. Big hug for you and your gf......believe it or not, things WILL work out. especially, and only, it you keep the lines of communication open at all times.