Hmm, serious post here. I sure don't know if I can help (probably not), but let's see if we can make some strange sense out of life.
First, the concept of karma only propagates wrongdoing by paying it back with more wrongdoing, and any thing good that is done only goes toward overcoming said wrongdoing. On top of that, can doing the right thing ever pay for having done the wrong thing? For example, would my saving your life somehow make up for taking someone else's? I've said it here before, but let me reiterate: karma is a vicious cycle that can offer no hope. Don't depend on it; otherwise you're pushing a car up a hill with a rope.
They say you can choose your friends but not your family...that's bull, too. It's all in who you hang with. Don't attack her verbally or physically or anything; just don't have to do with her or provoke her in anyway. The best way to tackle the aunt problem is with clean living...not to satisfy the demands of some horse biscuit karmic system but for your own good.
The way I see it, God lets stuff happen...not causing it, but allows people to go about things on their own within the framework He established before time. It's the double-edged sword of His deity. If He meddles too much, then we see Him as totalitarian and there's no free will on our parts; otherwise, we think He doesn't care and is capricious with our lives. In short, damned if you do and damned if you don't...if God could be damned, but anyway. You're right not to blame Him for it, but you should be careful in your approach. Remember, He's God, not the "Buddy Jesus" idea that people get in their heads....
Getting back to your aunt: she's chosen to act the bitch for one of two reasons: A) she's just a born bitch or B) she honestly thinks there's some wrong here. If she refuses to talk calmly and honestly with your dad about it, then you've either got A or you've got a bitterness issue at work. And that won't go away if you're all antagonistic...hard, I know.
That's where God comes in. He can change you, her, your whole family...even the whole situation. You've said how your grandmother has been strengthened. Everything I know about Him tells me that He is delighted to go to bat for His people and work on our problems. But you have to let Him know that you want to leave it to Him. He's not going to dump a million bucks on you to get you out of the bind, but He can and will soften hearts, arrange opportunities, and, above all, give you the grace you need to persevere.
The key is in becoming one of His own...while God blesses everyone in general who aren't (sun shining, rain falling, etc.), you won't get the grace you need to keep going and to carry on. The only way to do that is to see the need...and you have to ask Him to do so. The fact is, we all need to be saved from our sin, but we have to see that need before we'll willingly come to Him on His terms. Because a sinner is a rebel, the rebel must first surrender before God can do anything with him. The trick is having a peace negotiator who can go between us and God...and that's what Jesus does for us.
When you get here, He can work on your life from the inside first. That's where that clean living comes into play...doing so will, as opposed to tipping a cosmic karmic scale, please Him and open yourself to blessing. Whether those blessings come in the form of a bank error in your favor or reconcilation with your family members becomes a fringe benefit when viewed from the perspective that, unlike Conan, you really did find what's best in life.
I know others here may dispute what I've said, or maybe take offense at it. Don't knock it 'til you've actually tried it. But, E, I think this is your best and only hope at this point.
