To find this a bit rude?

[925XX]

My friend surreptitiously looks me up and down for several seconds when we meet and then on and off during our meeting. She also stares at me when she thinks I am not looking. But most of all the thing that drives me mad is when I am talking to her she leaves me mid conversation to speak to someone else without a "sorry" "just a sec" or anything else and after speaking to someone else she starts a new topic!

My SIL does this when speaking to me, she asks a question that requires an answer more than one word then will start another conversation with someone else nearby while I'm answering. I just stop and don't try to pick up anymore. I get she's uninterested deep down but feels the obligated to pretend to engage when I really couldn't care less if she spoke to me or not. I only see her once or twice a year these days. It's very rude.

That is not absent minded epilepsy, they are absence seizures. He’s not being absent minded. He is having a seizure.

I had a colleague who did this. She was a very vain woman and liked nothing more than to talk about the way she, and others looked : outfits, hair, nails, makeup.
I started doing it back to her. 🤣

Why are you bothered about the feelings of someone who is not bothered about yours? Have a think about that - why are her feelings sacrosanct?

Not only would I mention her behaviour, I'd be taking action.

For example, the "surreptitiously looks me up and down for several seconds when we meet and then on and off during our meeting." Point-blank ask her if she'd like you to give her a twirl so she can get the full 360. And state bluntly if she thinks her looking you up-and-down is subtle, it's not and you'd like her to stop.

And "she leaves me mid conversation to speak to someone else without a "sorry" "just a sec" or anything else and after speaking to someone else she starts a new topic!" is even easier. The first word out of her mouth to the other person, you walk away. Immediately. If she queries this (I just bet she will!) you tell her she ended the conversation. And you tell her she's being rude and you're BORED with it all.

Stop putting up with her shit. Better still, stop putting up with her.