Recommendation letter by significant other if you worked with them professionally?
No. If she discloses your relationship in the letter, the reviewer will likely disregard the letter completely, and may question your judgment for having asked her for a letter. If she does not disclose your relationship in the letter, that is a serious enough omission that it could have consequences for you later on (I can't quite tell where you are in your career, but the more senior you are, the more severe these consequences could be).