She's finishing college now and I want to live with her for at least 7-8 months before we get married. Everyone says you find out a lot so I want to go this route.
I would NEVER risk losing her over anything. Don't make a mountain out of a molehill here - this issue is peanuts compared to what I've seen in many relationships.
A bit conflicted? If you NEVER want to risk losing her, what are you hoping to find out in the 7-8 months of living together? How miserable a life you have to look forward to? Or, are you hoping to discover strange quirks about her (and she you) that need adjustment or some form of rectifying? Because if the latter, the situation you outlined is exactly what you would encounter by living with your SO, and if so, you shoud approach it as such.
You need to stand your ground. No need to be harsh or rude- just remain calm, explain the situation rationally- acknowledge her feelings and concerns, but remain
absolutely firm about your decision to go. Let her try to lay the guilt on you, but stick to your word. If she truly cares for you, and is capable of understanding logical reasoning when she has cooled down a bit, she will respect you more. If she does/can not, then you really need to decide if you want to be legally bound to this person. 2.5 years <<< rest of your life.
Assuming you do remain resolute, she may (will) be upset, but ultimately sticking up for yourself is something you need to get in the habit of doing. In any relationship, each person is responsible for putting the other in his/her place (in a calm, rational manner) when necessary- it is a part of communication.
This obviously does bother you, and if you let it go and give in, don't expect this kind of behavior to stop (on either of your ends). Better to put your foot down now and get the message across clearly and unambiguously, rather than letting her chip away at you until you either blow up or end up becoming some p***ywhipped wuss who she will eventually leave because you are "no longer the man she fell in love with."