[quote=@Flamelord]
<Snipped quote by Ploxerdon>

I mean, she doesn't have to. It's perfectly possible for her to kick his butt without showing off her NP. Because Tatsunoko doesn't have anything exceptional to keep her from just dodging the bullet and beating his face in with her fists. 
[/quote]

Theres also the thing where she is trying to bait the rest into thinking she is weak.
This might catch others off guard.
And she was also caught by suprise, and she doesn't know who is behind her so yeah...