Prenup = Prenuptual agreement, which is a contract two people sign before they get married, usually to determine who will get what in the event of a divorce. It's usually used to avoid lengthy and costly divorce proceedings.
Pension = An older type of retirement account
So, that ho on Instagram stayed married to him for two years, fulfilling the terms of their prenuptial agreement, entitling her to full divorce benefits, which will be about half of this guy's fortune, which should be enough for her to retire on.