The inventory (dated 1896) says it was given to "Princess Louise, Marchioness of Lorne, June 19, 1893."
So, it did go to "Louise Sr.".
The question now becomes, when did it go to "Louise Jr." ? Presumably, Louise Sr. could have been willed to her namesake, Louise Jr. Louise Sr died in 1939. Was the tiara ever seen worn by Louise Jr. prior to that date?
Another interesting question is: why was it given to Louise at that date? And, why in addition to the one given her as a wedding present?