Maine - domestic partnership to use health insurance

Hi, My partner and I live in Maine. We are both women. I am employed by a large company that has many locations across the US/the world, including an office in Maine that I work at. We are engaged to be married next year, but are not yet married. We do live together and have a joint lease.

Our open registration period at my work ended about a month ago, and my partner is turning 26 next year. The initial plan was for her to get something thru the marketplace once she turns 26. However, I recently learned about the law in Maine that domestic partners must have access to health insurance like married partners would:

https://www.mainelegislature.org/legis/statutes/24-a/title24-asec2741-a.html

I believe that we qualify under this law. I reached out to my work about it back during open enrollment, and they said that "eligible dependants include a legal spouse" so would not include my partner. However, I found that statute today and I do think we should qualify.

My question is: Would we indeed qualify under this law and would my work legally have to offer health insurance to her? Do we have to officially register as domestic partners to qualify, or would having a shared lease (as stated in the statute) be enough? And lastly, this might be a question for other places, but since we are outside of the open enrollment period, if this law does apply to her is it too late to get her health insurance?

Thanks