First, like PP said, we need to know her income and your income to make a judgment on how big of a problem 100K in debt is.
To me, 100K in debt isn't really the problem here. It's her ongoing lack of fiscal responsibility. The concern would be that if you marry, she'll just start spending more when she has access to your income, and pressing you to live in bigger houses, etc., and you'll be living hand-to-mouth for the rest of your life.
Or, maybe she just doesn't know how to be fiscally responsible, and if you teach her, she could change. #1 seems more likely than #2, but I know of people who have changed. It's not impossible. The thing is, you need to see that she can sustainably change for more than a few months.
You've only been together for a few months, but you say you love her. You need to sit down and have a serious conversation about this, explain your concerns, especially about her living beyond her means at present in a house. Does she realize this is a bad idea? Is she interested in changing and living modestly within her means? If not, you should probably move on. If yes, then see if you still love her in 12 more months, and get engaged at that point. Please don't get engaged in the immediate future, or worse, make a baby.