It's got a very 1970s-in-the-UK feel about it. I've never met one, but it sounds so pretty that I'd be inclined to avoid it. Maybe it's a latent superstition, like giving a child a name that's ugly or has a bad meaning so the gods don't get jealous and kill it. But I think it's just too risky. A
Cressida with limited social skills, bad skin and boring hair would be much sadder than an
Emma or a
Lily similarly equipped - just because there are so many of them, one can't form an impression of a "typical"
Emma or
Lily, but a "typical"
Cressida should really be poised and dainty - a state to which few can aspire.