I was brought up by a Tolkien nut of a father who passed it on to me in a slightly diluted form, so I lifted Morwen's first name from Tolkien's books when I was looking for a name for a background character for some roleplay in another game I played (specifically, the equivalent of a college roommate for my primary character at the time). Her last name came later, and really didn't come from the anime of the same name - I didn't even know about the show until some time after when a friend pointed it out.
Far as callsigns go, in Morwen's case the callsign came from her name - the dreaded "Morlag," patron saint of network latency - and actually was first given to me by someone who doesn't really roleplay all that much in EVE, but I've had the pleasure of RPing with in the game Morwen was a 'background' RP character for. I'm not actually sure how it went from there to the RP community - I might have just made a joking reference to it at some point and it stuck - it definitely started OOC, though.
Back to the original question, though - would I change her name? Nah. Probably not. It's a simple and easy-to-remember name, and even better, there's an amusing pseudo-etymology for her last name that works well for her given her hobbies and interests. (For those who haven't been told already, try taking "Lagann" apart as if it were in a Romantic language, then let google do the rest. It'll be pretty obvious when you find it - there's a reference to something in the real world that is also in EVE.)