Need help, seeking input, and feeling frustrated.

Currently I am caring for my elderly grandparent. Recently turned 96. She’s been on a “death kick” lately ~ and after speaking to her, was able to determine that she’s worried about expenses ‘when the time comes’ ~ legitimate fear on their part. Anyways, grandparent has two bank accounts (two different banks). I’m listed on the main one (can write checks to pay the household bills). On the second account her daughter is listed as main account holder. Well, one thing my grandparent has said... the account (@2nd bank) is specifically for her final expenses. I called the funeral director that she wants to use when the time comes. Spoke with the director’s wife. Ended up making an appointment to go down and “talk”. The wife knew why I wanted the appointment but she wanted to hear it from grandparent. And yes, grandparent said same thing to her. She signed a pre planning sheet. So pretty much have all the costs spelled out on the paperwork. Honestly, after that was done - all the “death talk” stopped. Well, got a frantic text from the daughter about the account earlier this evening... I tried to explain everything but oh my word - I got hit verbally in ways I never even imagined...

Starting with:

She was going to deposit money in account for head stone inscription of grandparent’s older sister - who passed away in 2012. To the best of my knowledge, aunt was the poa of the older sister ~ to include managing her affairs (money, etc.). Older sister had her own accounts.
Aunt was livid when she realized I was on the account - said/swore that the money was never intended for me - was in a trust for her. Thing to that being, grandparent and I went to the bank - we had a discussion with one of the branch managers. The original account was not totally closed out (still has $1,000). The second account has $5,000 in an irrevocable trust fund. Aunt then says (demands?) that I would need to open an account in my name. The money in that account (@2nd bank) doesn’t mean anything to me. I thought I was doing the right thing for grandparent. Aunt then makes a statement that she didn’t put her kids (my cousins) on the account - why would she? It doesn’t concern them. She then made it clear that she would ‘remedy this’. I’m at a loss for words...
Ironically aunt then made a statement that it was just ‘assumed’ (didn’t read the entire text, my blood was boiling) I’d ‘get the house’. Well, the house is already being left to me in the will. And yes, I’m prepared to deal with the idiots contesting it when the time comes...kinda sad that I was added on the account over a year ago and she’s just saying something now? Prior to me even knowing about the account...the account was listed as ‘idle’ (no recent deposits). Eh, I smell bullspit...
I don’t know much about costs for grave stone inscriptions, but does it really cost $6,000? Something (well, quite a few things) isn’t sitting right with me.
The funeral director’s wife is well aware of the messed up family dynamics (from drama earlier in 2017).

Grandparent’s name is on the account too. Grandparent opened it up and added the daughter. I have a sick feeling that the daughter is trying to blow smoke up my rear. I’m more concerned that she’s STILL running her mouth ~ as much as it pains me to say it.. I question the motives of the daughter - starting with, why didn’t she use the estate monies of grandparent’s older sister to pay for engraving of the grave stone? It’s been quite a few months and the daughter is just realizing this now? If the daughter was truly making deposits, she would have seen my name on the account. Grandparent and I spoke to the bank representative - they could see everything...they wouldn’t have made those changes if it wouldn’t be allowed?

(...had an incident earlier this year with a different relative calling APS and making up unfounded lies. When I tried to talk to aunt about the ‘guilty party’ who called APS - told to just ‘let it go’ and that she doesn’t believe the guilty party made the call. I know in my heart that the guilty party made that call... but as always, isn’t being held accountable for her actions)

Money truly is the root of all evil, it makes people do strange things.

Unrelated note: Despite everything (APS, etc) that was done...I do keep them informed about grandparent. While reading my emails, came across one from a step sibling ~ saying I’m a lazy pos who is sponging off of grandparent. I have no career (..been with current employer for over 9 years) and am a loser. The list goes on, but y’all get the point.
Figures the ones who have the most to say, can’t even confront me over the phone/in person, but rather by email ~ spewing all kinds of hate and lies. Go figure, when I try to talk to grandparent’s kids - I’m told to ‘let it go’, etc. Unreal, I’m expected to suck it up. But now if the tables were turned (cousins in my position) - would things be different?