These situations always baffle me a little. I understand everyone may be suspicious of motivations, and have misplaced anger and old resentments, families are complicated things, to be sure.
But how can anyone not see their anger should be placed on the dead parent who didn’t produce a will, or went around blabbing, what they wanted, without having done so, to only part of the family. The truth could not be clearer that they created the mess and deserve the blame. So I’d advise you to either keep your anger and resentment directed at them, or let it go.
As for the years of caregiving, another source of deep, stewing resentment, it seems, people need to be reminded to embrace their choices from time to time, I believe. No one takes on caregiving, long term, to outshine a sibling, or live rent free.
You take on caregiving because of who you are. Period. No one owes you anything, for doing so. You chose it. Reminding yourself of that, with help to keep you from having misplaced resentments. No one is obligated to support your choices. It’s nice, and kind, if they do, but they are not obligated by your choice, to do so.
Everything you’re ever going to be, you’re currently in the process of becoming. If you choose this course, (trying to screw her over, in retaliation for, her screwing you over), you may wish to look hard at what it is you’ll be ‘becoming’ as a result.