Betsy's Curse shard does not work as described. It does not spawn 3 aoe zones. Only 1. If you put down another whilst one currently exists it will be overwritten
It is working as described, the problem is your staff. If you staff fires more than 1 bolt, each bolt will create a zone. This means that you will only be able to ever have 3 zones stacked on top of each-other with a staff that has 3+ bolts per attack. After equipping a staff that fires a single bolt I was able to create 3 zones without issue.
However I don't think this is the intended design and it would be super if it was fixed :)