I had to make a trip today to the bank to pull out a large sum of cash--more than I could get out of an ATM, unfortunately--and my mom was with me as I wanted her with me for part two of the trip (I'm proposing to my girlfriend and we were going to look for an engagement ring).

My mom's always been very supportive because on some level she knew I was never really a female. I've been on T now for about seven months and the changes have been pretty massive. I'm past the point of being able to 'pass' as a female by any stretch.
Anyway, I was in the passenger seat as I figured it would be a little harder for the teller to completely see me. I begrudgingly signed the withdrawal slip with my legal name and handed over my ID that hasn't seen the light of day in months.
The teller chose that very moment to go into a lengthy spiel:

"I know she's sitting right next to you, but I would like to talk to ___ about getting an insurance policy through us! Her rates would be a little lower because she's a long time customer, is she interested?"

My voice has dropped to such a point that it's unmistakably male so I didn't initially respond. My mom had her jaw clenched tight and she blurted out, "He... ... ugh... 'she' isn't interested."
It looked physically painful for her to use the pronoun. The lady persisted. "Is she sure becau--"
"Yes, I'm not interested, thank you."
Mom said she got this odd look on her face when she heard my voice and slid everything into the drawer quickly.
"Have a nice day, guys" was all we got after that.

As we were driving off, my mom looked over and went, "God, that really pissed me off. I just wanted to tell her to shut up and hand over the money. It was really hard for me to have to say that about you and I'm sorry."

We had a little discussion and I think that's the first time that it became truly apparent to her that I'd been dealing with those feelings for years throughout every single interaction. She came out of it saying she had a much deeper understanding of what being trans must feel like.
On the flipside, it reminded me that most people don't ever have to think about these scenarios and happenings. It's weird how these definite truths for us are so alien to others, isn't it?

It's really cool that it clicked for your mom like that.

It may have felt awkward, but -- wow. How great for your mother (and for you) that she had a moment like that, when she "got it" on a gut level about what it's like to have to deal with that stuff, day in... month in... year in and year out.

That's amazing that your mom is so understanding.  Mine tries, but she calls me by my birth name and female pronouns by accident at least a couple times each time we interact.  She usually corrects herself, but I would give anything for her to understand how much it bothers me.