That's the great part. Got to beat a fairly hellish boss to get the needle upgrade, and then it still takes six hits to defeat all the enemies in the new area, rather than eight if you'd skipped it. Got an unusually easy runback to her, though, so don't claim the designers don't give you anything.
Just got into act 2. Thought they might have gone easy for a bit after the hellish end of act 1, but no, straight into much harder.