Normally group data is not send.
The EVENT_INVENTORY_SINGLE_SLOT_UPDATE triggers with the InventoryUpdateReason INVENTORY_UPDATE_REASON_DURABILITY_CHANGE.
As there is no special update reason for the group repair kit I guess you cannot differ from a self repair by using a kit at your own char, or any group triggered one.
Maybe a group repair kit triggers any other special API.
I haven't found any though.
If all group members use the same addon you could share the "usage of a group repair kit" via
https://www.esoui.com/downloads/info...oupSocket.html