This is more of an ESH than a N-T-A.

She should've never have introduced you as her boyfriend. Even if the root of the problem was that neither of you clearly communicated about what you were looking for, she crossed a boundary by telling them that without even confirming with you first.

That said, almost no one considers a widower married. No one can tell you how to live your life because there's no one way to do it, but this is weird thing to expect others to intuitively get.

You spent a lot of alone time with her, and as someone else mentioned, if you're both religious, it could of very well been miscontrued as respectful dating/courting. It's also not unusual (at least with some of the men I've met) for someone to reference their spouse often and still be interesting in dating and remarrying

Though if the roles were reversed, my judgement would be the same.