Harley is definitely not letting Amelia grab away the bat, and tightens her grip on her weapon as not to lose it.

When the dagger is tossed at her yo-yo, Harley does another fling of the smaller weapon, hitting the dagger in midair. She has Palmer to thank for creating the strong metallic yo-yo for her. The nice thing about a weaponized yo-yo is that she can throw it... and the weapon returns to her. It has a reinforced string too.

And then she flings her yo-yo again, aiming for Amelia's throwing arm this time.