Should I Give Her The Marriage Ultimatum?

My gf and I have been dating for 5 years now. We have had a child as well. In the last five years we have bickered, argued, enjoyed, loved, screamed, had fun and everything else you can think of. We have had a seperation once do to her, not me wanting "a break". (Long story). Anywho, I was just recently baptized and the day of my baptism, our Pastor's sermon was over cohabitation before marriage. Boy we both felt awful. Well, the overally outcome was that we were habitual sinners by continuing to live together as an unmarried couple. Now don't get me wrong, I don't just want to marry her b/c of that or our child. I have wanted to marry her for some time now but her young dreams (delusions) of a spectacular wedding has held us back. There not enough, not even close to the ideal wedding she wants. Well now it's not the grand stand wedding that's causing the delay. She feels we aren't ready to get married b/c we bicker/argue too much. She feels as though we shouldn't always have to try/work at our relationship, that it should just work. I try and reason with her that regardless of who you are or where you are in life, you always work/try at the relationship. No relationship is perfect but you work at it to try and be as perfect as possible. She isn't listening to that. We both love each other dearly, if not, we would have broken up a long time ago. I'm getting to the point where I am wanting to give her the ultimatum. Say yes, we'll get a dress. Say no, time for me to go. Should I use the ultimatum or just continue to wait it out?