<Snipped quote by Guardian Angel Haruki>
She's a redcap, which are pretty formidable on their own. She knows Bavlorna's weakness, which will make the hag much less formidable than she would be otherwise. And she'd have six other people backing her up, providing the strength and safety of numerical superiority.
A case could be made that she would have a good chance of taking out the one she hates the most and living to tell the tale if she helps out.
And before you go saying that she could have all of the reward and none of the risk by just staying in the kitchen, consider this: Would listening to a battle happening in a different room really be as satisfying as being there in the action, seeing the look on Bav's face as her weakness is exploited, and bathing in freshly spilled hag blood as seven people rip and tear until it is done?
All of that is correct. You have a point.
However: Bloody Toes is in an interesting situation.
1) She was working for Bavlorna, being paid in victims, as her butcher. That's a great gig for her.
2) If she knows Bavlorna's weakness, then she knows what Bavlorna Blightstraw is capable of.
With these two factors in mind, she knows that if the party fails to kill Bavlorna, and was seen helping you guys, then she's going to face consequences worse than just losing her current job.
So, yes, her blood lust would be satisfied if she helped you guys, but she's aware of short term and long term consequences.
With all of this considered, Brutrumukk can roll a Persuasion, but it would be a straight roll.
Yes! 
