What should I opt for bipolar depression, Lamotrigine or ketamine infusion therapy?

Hello doctor,

My wife was previously diagnosed with bipolar II and was taking 100 mg Lamotrigine daily for depression maintenance. She was on that dosage for nine years. She recently suffered a more chronic depressive episode and went out of town for ketamine infusion therapy. The infusions were very successful, and the psychiatrist who was assessing her for the infusions suggested that she did not need the Lamotrigine, that it was ineffective for treating depression in bipolar II. She tapered off the Lamotrigine, which was very difficult. It has been three to four weeks since her last dose of Lamotrigine, and nine weeks since her infusions. She is feeling very moody and depressed, irritability, fatigue, loss of focus. The question is, do you think she needs to go back on the Lamotrigine? Or does she need to get a booster shot of Ketamine? Both are difficult solutions. Getting off the Lamotrigine was awful, and getting Ketamine requires out of town travel, etc. Kindly advice.