Hi Jamie J
I had my first stash when I was about 9-10 years old and it was a pattern I would follow for many years...There were very few times when I got the chance to actually wear any of it but just the "having it" seemed to help me a little. The fear of being caught , guilt, self-doubt ,shame and the list goes on as described by Dena, are the reasons it is hidden. You my dear are a very special person...it takes courage and true love to take the time and make the effort for your partner in the way that you have. Have a big hug from me, You are doing great. It is clear you really love her and want to understand why she does the things she does.
Sarah T