girlfriend/spouse
So if you've been with someone for years or even decades, you've got kids or even grand-kids together, you still think you should hide your bitcoin activities from them? Maybe a new partner or spouse you've been with for only a few months, sure, but at some point when you build a life with someone, you share your finances with them.
I'm one of the strongest privacy advocates on this forum, but at some point, this just becomes common sense to let your spouse know. Why would I want to risk me suffering from memory loss or dying and none of my family being able to access or benefit from my bitcoin? My wife is fully aware of all my wallets, all my back ups, all my security, etc. Why would I want to keep that from her? If you are having so many doubts about your relationship that you think you need to keep a large part of your finances completely hidden, then you should have signed a prenup.
Unfortunately I don't think a prenuptial agreement is enough to protect your assets if you are wealthy and if your spouse meets an evil lover. If she knows all your backups and your security tricks, she won't even need to steal them herself, she will just need to explain it to his lover and he/they will be able to steal your funds when you're out. Moreover you can't be 100% sure she won't repeat all those critical things to anyone else, especially your children if you have any. I wouldn't recommend that, I agree with Wind_FURY, it's not safe. There are way safer things to do if you are concerning about your legacy or a memory loss.