In the state of New York can an 18-year-old who is still in high school and living under her guardian's roof get married to her 25-year-old fiance without her guardian's signature?

I actually don't know. However, if you can't get your guardians to approve of your fiance, you may want to take a step back and really take a good hard look at your relationship and ask yourself why they don't approve. They may just be trying to save you some heartache.