Apparently she wasn’t elected. Appointed.
That is correct. The governor of the state of Maine is elected of course. Other cabinet officials are selected by the political party that has a majority of the total members in both the state house and senate which of course is the Democrats. There is no lieutenant governor in the state of Maine, so the Maine Secretary of State is next in line.
Bellows ran for the US Senate against Susan Collins in 2014 and got about 30% of the vote. If you read her bio in Wikipedia, it will be obvious that she is pretty far left.