Wow! Can't believe that this name isn't that common! I thought it would be like Andrea and Alondra, but much more rarer! I LOVE this name and so does my sister.
I /personally/ LOVE this name. I am currently planning to write a story with the main character named Leandra. I think the meaning would be 'lioness' or 'lion of a woman', as it's the feminine form of Leander, which means 'lion of a man'.
Leandra is used in Spanish, Portuguese, and Italian, although it's not too common. It is NOT a modern creation, and it certainly isn't a combination of Lee and Andrea. I do like Leandra, but it certainly is not an English name! [noted -ed]