How can I quit obsessing about the things my elderly mother keeps bringing up about my past, how I look and how much I paid for things?

It's extremely draining listening to the constant negativity once the filter goes. Rude comments made about people in public so that they can hear them. It's so embarrassing. Then the prying questions into your or your siblings business. I dread having to see my father who is unfortunately not in care, and will NOT go, and I leave him with my guts tied up in knots. He doesn't care one bit that I'm badly affected by his behaviour. Sorry I'm venting. This isn't helping you.
The hard part is being the sole caregiver with siblings who don't want anything to do with our difficult elder, and who don't care if we're the ones having to deal with it.
So God Bless you and try to be strong as I will.

Sometimes I think it’s sheer boredom, other times I think it’s just being nosey. For what? Only to criticize.

It’s different if a person is asking questions in order to help. That’s fine, but to ask for no reason other than being nosey, then it’s is an entirely different thing

I hate all the comparisons too. Everyone has different circumstances and feelings.

You could turn the tables on her. For instance, if she asks, “What does that costs?” Say, “Are you going to pay for it?”

It is annoying to feel like you’re being interviewed or worse, being interrogated.

My brother is retired law enforcement. He speaks to everyone like he is interrogating them. His children barely speak to him because it’s so uncomfortable for them. It’s sad. It isn’t a natural flow of conversation.

What makes people think they can pry? Just strange. Then you have some people that ask the same question, ten different ways. Do they think we are that stupid? Guess so. They get really frustrated when they aren’t answered no matter how they phrase the question.

If we ask them a question, they will answer the question with a question or start talking about something totally unrelated. It’s nuts.

I wouldn’t visit any more often than you are comfortable with.

If my mom would constantly ask me about this one or that one, I would end up telling her, “You have their phone number, call them and ask them.” I hated when she pumped me for information.

With my mom, if I changed the subject, it didn’t matter, she would go right back to the same topic so I would have to be direct and say that I was not going to discuss it.

I would nip the sister comparison in the bud with a simple...that is nice she has the extra income for those things, I do not so that is that.

My sister took my mother on holiday to her condo in Florida. Mother raved about it for MONTHS. She particularly liked that Sister had "a wardrobe you can walk right in to!" I wittily riposted that I could walk into my wardrobe any time I'd had too much to drink ho ho ho but this brilliance did nothing to dampen mother's enthusiasm. Truth is I couldn't compete, either, and it made me catty.

Stop worrying that you are being unfavourably compared. Perhaps your sister has a secret sugar daddy. Perhaps she has more money than sense, or a pal who's a florist. Good for her! Meanwhile, you are doing your bit - you dutifully turn up and pay attention to your mother. But no matter how dutiful and dull your visits are, I will bet that your mother doesn't value them one whit less.

You don't like your mother asking intrusive questions; but then you say that you have nothing to talk to her about. Well, if your mother is losing filters (it does sound a bit like it) this is a great opportunity to dig in to your family history and mine her for personal recollections. I was on the verge of hearing all about artistic communities in the 1930s in Paris, and agog to know more, when my great aunt suddenly remembered herself and went all "not in front of the children" on me, so I never did get the full juicy scandal and now I never will. Don't miss your chance!

Or, what do you talk to other people about? Pick your own topic of conversation if you don't like hers, and see if that proves more fruitful.

If you resent how much the travel costs, could you teach your mother to Skype and call her more often instead?

From your post I gather that you do have anxieties about managing financially in general, and I can sympathise with that. I know, too, how galling it can be when other people's problems are ones you would love to have (another family member was heaving sighs about how difficult it was to decide what to do with the second home she and her husband found they weren't using, the poor dears) but you really do have to separate out practical problems, which you can work on in your own time, from your feelings about people who don't share them (and, perhaps, in your opinion don't know they're born).

Your mother isn't trying to turn you and your sister against one another. It's natural she would talk to you each about the other, and it's natural that she wants to know how you're situated. Whether or not you feel like telling her (or telling her to get lost, come to that) is up to you, but don't feel that her wanting to know is a judgement or a criticism.

If she asks about something that isn't her business, tell her that it's not her business. If she pushes, tell her it's not her business and quit being so flipping rude. When she carries on about what your sister brought her, say, "That's nice" and change the subject. There is no excuse to be rude, no matter how old you are.

Boundaries.

There is no need at all to tell your Mum anything about your personal finances.

If she asks, look at her and ask how that could be any of her business?

The same applies to any other personal questions about you or your family.

When Mum talks about your sister, agree that it is very nice that sister is able to do these lovely things for her. And leave it at that. Don’t engage.

As to where your sister finds the money, that is none of your business, just as how you spend yours is none of Mum’s business.

It is hard to disengage and set boundaries, but it is worth it.