Buffy fought Glory at least twice without that hammer, and managed to stay conscious. When they first meet, and in "Blood Ties."

And I didn't mean to imply that's the only way to win--clearly it's not since Buffy won with the standard human strength of a 5'3" woman under a hundred pounds. Also, due to her size, proportionally, she'd have to be much stronger than Spike because she is so very, very tiny.