Belly attachment ladder breaker
If she connects with a plain table shape. Black can connect and capture the top.
If blocks, then can cut because the ladder is broken: if Black A then White B makes 3 liberties against 2 for Black's cut off stones. If Black B then White A is next escaping or putting B in atari.
Can Black also play a double purpose move like this one?
No, up to White B the black stones are caught in a loose ladder.