The only people you can trust on this earth are probably your parents and then your spouse, and trust your spouse if only you know he/she is trustworthy because you have been together for years, and it should be easy for you to understand that when you are living together.
In my case, I trust my parents, so it's not an issue for me to share personal details about my finances with them, just like they share everything with me. But that is my case, therefore I can't say every parents are going to be trustworthy and loyal to their children, because there are situations where parents took advantage of their children and even commited crimes against them, while the opposite has also happened in other situations.
To tell people to not trust anyone is too extreme. I think you have to discern who you can trust from who you can't. At some point in your life, inevitably you have to trust someone, otherwise you are going to have a hard time doing business, making friendships and building a professional career.
I would avoid talking to women about personal finances, though. If you don't avoid, it's going to be pretty hard to conclude if she is interested in you or in your money.