I love the idea and it looks promissing but...there is certain reason for some parts of our life to be separated from our "second halfs"
You may be lucky but imagine your girl does the same thing as with food she makes. You say it tastes delicious to make her pleasure even if sometimes it's not a best "take on the pie". Now with guitar...imagine somthing goes wrong, you don't tell her and later then she asks you over and over why don't you play her guitar. Is something wrong with it?...and now poor you...trying to find an excuse without saying the guitar is not as good as you told her for the first time
Oh...but if everything goes ok I can only suggest to change your name for "Gabriel Jaguari"
hahaha I can get the point. This won't be a problem. We are completely honest with each other and this is mostly a hobbies for her. He also sings and has her band, and she know that when talking about music I'm honest with her and his band.