I`m sorry, I just cant get over the `triste` part of it. Maybe if you were writing a fantasy story you could use it on a character, but I wouldn't saddle a kid with this name. I know other people have talked about
Sadie and
Madeleine but those names don't inherently MEAN sad or mad. Someone also mentioned
Cecilia which means blind, but in this case at least the meaning isn't obvious from the name. As a French Canadian, as soon as I see it I just think "sad
Bea" and someone with this name would give that impression in any French or Spanish speaking country (which is quite a few places).