What does it mean when yor cat is purring, and then you're playing a computer game with noise and your cat starts walking all over you, and gripping you with her paws, and nipping you? It's rather cute, and annoying.
It means they want attention! I don't know your kitty well enough to know if she wants pets or play - but they often do pick the most inconvenient times to want our attention. Of course - when we want a kitty on the lap to love on, or a kitty to run and play with us, they're nowhere to be found.