Look, I get that you feel guilty setting boundaries with this lady. So does everyone else. But, as a deeply religious person myself, this woman is violating many, many tenets of most major religions in the way she is treating people. I don't know what religious tradition you belong to, but most have common ground on these things.
1) Treat everyone with respect, and love/generosity means putting others needs ahead of your own. HER time is hers to give to the "needy", but YOUR time is not. By trying to make YOU wait, she is being selfish.
2) Taking/stealing from others is not holy, generous or sacrificial. It is wrong. Even King David refused to give an offering that he did not pay for. (See 1 Chronicles 21:24 )
3) People who do honest work deserve to be paid for it. 1 Timothy 5:18 (the worker deserves his wages)
4) If you make an agreement, honor it. Don't attempt to change the terms of the deal to suit yourself. (Let your yes be yes, and your no be no/use honest weights and measures)
5) Don't manipulate, bully or intimidate people into doing what you want. Attributes such as "discord, fits of rage, hypocrisy, slander, deceit and accusations" are not holy behavior, but the opposite. Gentleness, respect, thougtfulness, orderliness, and self-discipline are the goal of religious service.
Hugs, I know my quotes might not be directly applicable to your situation but they are the most accessible ones I have, and I don't think they are controversial?