(get) engaged, pledge to be married; betrothed.
engaged - Definitions from Dictionary.com
[1] She
will engaged Troy within thirty days.

[2] She
will get engaged to Troy in thirty days.
Note,
Get engaged within 30 days
Meaning: some day between today and 30 days from now--inside of 30 days; e.g., she and Troy will make a pledge tomorrow or in two days or next week, that they will marry each other on some day in the future that has yet to be set.
Get engaged in 30 days
Meaning: thirty days from today;e.g., today is the 7th of June, so she and Troy will make a pledge 30 days from today, on July 6th, that they will marry each other on some day in the future that has yet to be set.
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