Who's to say she wouldn't if she had too? Sakura has shown complete devotion to protecting the ones she holds dear.
She forgot to breath in madara's presence, how would she fight. Naruto was dying, what if madara attacked him? She was paralyzed in fear. U_U
What about when she cut her own hair granting herself freedom from the grip of someone much stronger than her? Then preforming a series of attacks that were meaningless?
Cutting hair? Lol that isn't much and like I said before, I never stated she was a coward just that she wasn't the bravest.
Diddo? Didn't Sakura charge Garra with nothing but a kunai knife? Was someone backing her there?
She didn't charge gaara, gaara charged her and she pulled out a kunai to defend herself and sasuke.
She charged Naruto while the 9-tails took control of him, even after notating that the chakra that was possessing him couldn't be controlled. She was fully aware of the danger she was in but decided to proceed with her actions.
She didn't charge naruto, she was trying to get through to him, while she was aware of the potential danger she didn't fully believe naruto would strike her.
If you think she is so fearless against a possessed naruto, why didn't she try to "charge" him when the possessed naruto was fighting pain? Because she knew she wouldn't be able to speak to him and would be killed in an instant.
I will say it again, she isn't a coward but she is far from the bravest.