Like Caseh suggested, [A+B] may help in both of those situations, if you aren't using it. It starts with a Horizontal, and if you charge it up it will leave you at advantage on block. If I recall correctly, 6A+B also leaves you at advantage, but I honestly haven't used the move very often in battle. I don't know how well it counters step. Something I use rather often to counter defense is 6AKA_B. The A followup is low, and the B is mid. The B also takes a while to land, so I've found some people inexperienced against Hilde will try to mash out a move ad get hit hard for it. Both followups are rather unsafe, being -15 and -16. You won't get launched for it or anything (unless someone has an i16 launcher I didn't know about?), but you may eat an AA or something similarly quick if the opponent knows this.
Oh, and don't underestimate Hilde's A unblockable. At i37, it's one of the fastest in the game and does fantastic damage.