Stop.
You have NO idea what any person sitting is going through. You have NO idea if they are rude, blind, have balance problems, just had hip surgery, are dealing with an asthma attack and just trying to get back to the room, etc. No have no idea about anything.
And I, when pregnant, HATED sitting. Sitting hurt. Getting down to sit hurt. Getting up from sitting hurt. I liked to stand. If I had known what a Disney fan I would become later on and had gone to Disney, I would NOT have sat down.
On buses I got to deal with people INSISTING I sit down, and being ridiculous when I said "no thank you I prefer to stand". Like people continuing to stand, like I'm a feeble stupid woman who doesn't know what I need/want. Just being ridiculous.
When DS arrived and I wore him everywhere, he HATED being in the sling/Ergo when I was sitting. So much hatred for sitting, LOL. So we stood, again. And again, people wanted to insist that we follow their program, and again did silly things when I refused to sit simply because they wanted to be gallant. Your gallant agenda doesn't change my own wishes and needs.
So one, don't insist on someone sitting just because you THINK they should sit. Live your life, sit in that seat, don't be ridiculous. And two, don't assume from the outside appearances that a person CAN stand to relieve someone else.
ETA: we rent a condo in a building that is mostly very senior citizens. Our next door neighbor is in his late 90s. He is vital and amazing, and I cannot imagine him EVER sitting on a bus. So just because you're elderly doesn't mean you WANT to sit, either.
Whereas my MIL was old before she was 40. By the time I met her (she was just over 60, I believe) she had had two heart attacks. Now she's had at least 2 more and at least 6 "mini" strokes. She LOOKS healthy. She's not. She doesn't look anywhere near 75, either. You might think she's able to stand, but she really should not do so when on a bus.
20 years younger than my neighbor, but a universe of difference in health between them.
Oh I'm SO sorry. My mom died at 55, too, it's just a brutal age to have moms taken from you. In my case I had just turned 30, my life was finally turning around out of my silly 20s, I was looking forward to the rest, and wham. No mom. Brutal. I'm so sorry.