I would consider it a female name, though I do think it could work as a unisex name as well.
Linden is also a surname used in Scandinavia, not too unlike the Swedish surname
Lindén. Where I'm from it sounds too much like exactly that, a surname. I do think it would work well as a first name in the English speaking world though.
I have a cousin named Linde (lin-DEH), which could be an alternative to
Linden. I know it's not the same, but I'd say it suits her well.