It seems like this is a good place for dynamic equity. It's really handy to have B around but you don't think she should have a defined share, and you don't know how long she will stay around. Why not pay B in slices for funding when it happens (with an agreement now on the rate). Start off with a commission on that lawyer work. As for the other work and meetings, pay a fair wage and work it into slices.
If B has a good chunk of the company that she feels is fair, she will push her contacts to come through in the clinch.
In my current fixed equity company there are two 1% owners out there who helped a lot in the early stages, they deserve something. I would have rather had it dynamic, with the 1% they did their chunk of work and saw no more profit and went off to something else. Had it been dynamic they may have looked for more ways to help.