I changed a new clothing mod into an esm. Then I went into the CS and selected the esm and my esp. I opened the NPCs inventory and deleted the current clothes. Then I copied new clothing from the new clothing mod to the NPCs inventory and Saved. Started the game and went to the NPC and she was wearing the previous outfit. Use the Active Inventory spell and I could see only the new clothing I had added. When I exited her inventory, she suddenly wore the new clothes.
How can I get this to happen without my interaction?