Hope this helps, it's from a legal dictionary.
A widow's interest (sometimes just a life estate) in real property owned by her deceased husband.
At common law, "dower" is a right which only vests as of the death of the husband, and was limited to one-third of the husband's real property.
Historically, this referred to a husband's obligation to support his wife for her lifetime and in heraldic vocabulary, the word dowager when placed in front of a woman's name meant that she was a widower living off a dower.
So it looks as though if she remarried she would lose half of her annuity and all of the income from her deceased husband's estate