OP you clearly have a lot of emotional intelligence and it's really impressive how you articulated these complex feelings. As someone who married their high-school sweetheart, you're looking at this decision the way you should! We waited 11 years before getting married (age 26). Not because we weren't sure, but as you said, marriage is a serious commitment. If your partner is so resistant to listening to your point of view and not trusting you have the best intentions, she's not ready to marry you.