I waited in Onira. After 12 days Ira's 'holding' status was gone and she appeared in Onira. Maybe this waiting period could be eliminated or at least reduced.
Also, I tested this issue by marrying other NPCs. I can confirm this issue occurs only when the NPC leads their own party. I didn't experience any issue marrying Vasilia who was located in the lord's hall in Lycaron and not leading a party. Thanks for your support.