In the Star Wars Legends continuity, the Second Imperium Crisis was a major conflict in 23 ABY between Luke's Jedi Praxeum and the opposing Shadow Academy of the Second Imperium. Most of the conflict takes place in the "Young Jedi Knights" series of YA novels.
Luke is a prominent character, appearing in every novel, but his wife Mara Jade never appears. If I understand the chronology correctly, she and Luke had been married for around 3.5 years by this point, and Luke was personally helping her train her Jedi skills. During this time, she would presumably be living at the Praxeum with Luke. However, during the 8-9 month period covered by the books, Jade never appears or gets mentioned by other characters until the VERY end of the last novel when the Solo Twins become full Jedi Knights.
Where was Mara Jade during the Second Imperium Crisis?
Note: Mara Jade's whereabouts are known in 22 ABY (when she fully commits to Jedi training) and again in late 23 ABY (when she appears at the Solo Twins' graduation ceremony). This question is about the time in-between those two events.