Makeup: How do you apply?

Have you noticed that women are particularly sensitive about makeup?

Most girls reach their twenties with some version of training, whether it be years of watching Mum in the bathroom before she goes out, or a girlfriend sitting them down when you're 15 and applying peacock blue to the eyelid, or applying that same eyeshadow yourself as a six-year-old in plastic high heels.
I also have no doubt whatsoever that some women reach their twenties without any knowledge whatsoever of how to apply makeup. These women I think end up being self-taught, and you may know some yourself.

I have twin cousins now in their thirties that have still never really been taught how to apply their makeup. They muddle through it of course, I've seen them both in makeup, and its probably a combination of a quick lesson from mum, watching friends over the years and trying it out in the mirror. They recalled being in their teens and their mum (not being a huge makeup person, but having two teenage girls who might be keen) she offered to send them for a makeup course. My mother never offered to send me for lessons in makeup, and I'd like to think I would have leapt at the opportunity (in the manner I would now) had it been offered.
My cousins turned down their mothers offer, and now in their early thirties, probably wish they hadn't. One of these cousins was invited to the Arias last year, and asked me to do her makeup! I was surprised, I haven't done anyone's makeup for quite a while, but its essentially the same as doing your own, just it takes longer. I'd never noticed that she doesn't really wear makeup, and it's because she doesn't trust herself to do it properly.

I think when it comes to makeup, a little knowledge goes a long way. In the next day or so, I'll list some of the tips I've picked up along the way.

What I've noticed though, as I started with, is how makeup is quite a touchy subject amongst women if you want to be critical. Some women, while they may admit to a close friend, that they don't know much about makeup, don't necessarily want the greater world to know that they're a bit clueless. They certainly don't want you pointing it out to them!

Way back when I did my makeup classes, I gradually learnt how to apply, and what to look for etc. It was at this time that it gradually dawned on me that my own mother wasn't applying her makeup "properly". I tried to speak to her about it, and this was my first time where I realised some people simply don't want to hear about the way YOU do it.
Her method works just fine for her, and while she took a few things on board, she's essentially got the same style as before, and who am I to interfere? It works for her.

I find the dilemma of whether to tell someone about their makeup malfunction, akin to the "dress in the skirt" or "toilet paper on strangers shoe" dilemma.
Both of these predicaments, if you saw, you would probably tell the person wouldn't you? But there's a line we cross when we do that. Stepping into this strangers life and telling them something is not quite right, to save them the embarrassment later.
I personally would be mortified if I went out, as a friend did recently, with a foundation line on her jawline. Blend blend blend I think when I do my own. If I hadn't blended properly, I would want someone to step in and tell me, discreetly of course.
Of course the older a person gets, the less they want to hear about what they're doing wrong. "you mean I've been doing it wrong all this time!"
I had my colours done several years ago and there was a woman in the group that loved pink. Now I quite like Pink also, but I wasn't quite so into it at that point. This woman only wore Pink, and mostly it was a baby pink sort of shade, very feminine and she liked it that way.
She was told she "couldn't" wear that shade anymore. It wasn't that she couldn't wear pink at all, but she discovered she'd been wearing the wrong shade all these years (she was in her forties). Pretty devastating for her really.
So back to makeup though, this friend of mine recently had quite the foundation line going, and I just couldn't bring myself to tell her. Of course, I've been told I'm not the most tactful person getting around also, and I didn't want to offend her, and she's a very good friend of mine. So it made me think who COULD I tell? If I can't mention it to my dear friend, what hope do we have?
Why are women so sensitive about the way they do their makeup?