Well I know of one woman who has worn one on her thumb for many years and she's not a lesbian and she's racist as hell so go figure. I guess it means many things to many people from no significance at all to some special meaning. Depends on what part of the country you're in sometimes maybe as well. Hard to tell nowadays. Geeezzz.
White women who fuck black guys love the spade symbol...♠
Now, the lambda thing is pretty widely known within the lesbian community and is pretty exclusive to lesbians...meaning that straight white women don't go out and get lambda tattoos or wear lambda necklaces. So if you see a woman with a lambda tattoo or jewelry, you are wasting your time trying to work them, unless you have tits and a pussy.
The spade thing is less exclusive and thus, is more likely to be sported by women who have no clue about the supposed connotation associated by the kool-aid drinkers. I was with a girl one time who was shopping who saw a shirt that had a bunch of designs on it, but it was dominated by some spade symbols. She said that she liked the shirt and I told her that some people thought that white women who wore anything with a spade on it liked/fucked/dated black guys. She looked at me like I had just asked her to rebuke Menachem's Razor. As I had suspected, she had never heard of this association.