DD14 is regularly assumed to be trans/NB/a boy - any advice on how she can respond?

I think that 'I'm female' is going to be more helpful than 'I'm a girl' or 'I'm a woman'.
Oh, maybe. Or maybe for a couple of years around 2018 it was more helpful, before TW started claiming to be female too.

Men also change as they age. Even the butchest older women don't look the same as men the same age as them due to men having stubble.

The differences between male and female , facially , is less different between teens if boys are yet to start shaving.

Of course, people could be aware she is a girl and mistakenly think she is presenting as a boy . They either think they are doing the right thing by checking if she uses alternate pronouns , or they are being rude / after confrontation .

I think that 'I'm female' is going to be more helpful than 'I'm a girl' or 'I'm a woman'.

I find smiling and saying 'morning' or something generally does the trick. When people get a good look at your face they can tell, and voice helps too - even if low for a girl, it will be high for a boy that age.

In the case of someone challenging in loos, she just says 'I'm a girl' - again with a cheery smile. Actually in loos this is going to be an absolute rarity because being in the women's loos shifts the base assumption to female until proved otherwise. Smile can make sex more obvious somehow - maybe shows up different aspects of your face? But it would also make me smile because I am happy people are looking out for women.

Direct pronouns question I'd suggest she just says 'I'm a girl'. Tells them what they want to know without playing along to the pronoun silliness.

As a lifelong tomboy, and definitely female, I now say something like 'Been to Specsavers lately?' But your DD could just say she's a young woman?

This is the result of several years of trans ideology being pushed onto us all - many of us are hyper aware of the potential of finding unwanted males in female spaces. Many years ago when I was young, we all wore androgynous clothes and had short hair and no-one batted an eyelid - as it should be.

I can imagine how difficult this is for your DD - perhaps just saying ‘it’s ok, I’m female’ if anyone says anything? I’d avoid saying woman, that seems to cover anything men want it to sadly.

In toilets if directly approached or confronted I would perhaps go with the "oh don't worry, I'm female!" in a breezy tone.

In terms of asking pronouns, I think that's just because it sounds like people genuinely cannot tell her sex from what you say. And that's just seen as a more 'polite' way of asking than juer saying "hey are you are a girl or a boy?" I think people often feel embarrassed when they can't tell someone's sex. I would just respond telling them she's a girl and that's that, no need to specifically go along with the pronouns thing, particularly in situations where you say she's the only person being asked. That is just people asking what her sex is without wanting to seem rude I think.

I'm totally with you on it all btw OP just for avoidance of doubt! Completely not the same but my DD is only 6 and between age 3 and 5 she had a pixie cut. Obviously little kids all look the same so not possible to tell her sex but people always, always, always assumed boy and that was the even the case if she wore an entirely pink outfit or a dress or sparkly shoes etc. People would always assume 'boy in dress' rather than girl with short hair. Which I thought interesting.

WallaceinAnderland -- i think it's very common to be bothered by it! I am 6ft and was often called young man in my teens. I was shy and found it mortifying and as though i was less of a woman.

thankfully it sounds like OP's daughter isn't feeling this way, but it can still be awkward. Hope she gets more used to it soon OP and can feel confident. (it gradually happened less and less to me, and i minded much less as time went on too)

My friend used to get this around that age but it stopped as she matured. My son used to be mistaken for a girl sometimes when he had long hair and again it stopped as he matured.

It's not that uncommon but it is uncommon to be bothered by it. Tell your dd to just ignore it or if anyone says anything just correct them. It's no biggie. They made a mistake, I'm sure she's made mistakes in her life too.

I’m guessing you don’t have many contacts who are currently in secondary schools. It’s a very different world compared to real life. I have 3dds and it’s a big thing, especially dd1’s year group. She’s year 11 and interestingly was in lockdown for year 7/8. I wonder if that impacted. It’s slightly less intense in dtds year 8 group but still there. It is not “cool” to use the pronouns “she/her” and they are all “they/them”. It gets very confusing. Dh was worried dd1 was going to Ethan‘s for a sleepover and was surprised I was so cool about it… Ethan (he/him) doesn’t have a penis. Dh now fine with the sleepover. Parenting teens right now is a new minefield of social media and gender ideology.

Yes I'm afraid this is where we are now. You can't be an androgynous looking girl anymore without people making assumptions. I hate it.

I hope your DD is ok OP because this was a factor in mine identifying as trans. She was young and vulnerable (and autistic) and people constantly calling her "he" contributed to the confusion.

The idea that to be a girl you have to have long hair and look girly makes me mad. I got called a boy occasionally as a kid but now its so much worse.

Anyone who makes those kind of assumptions about her is being sexist, because they think that you can't be properly a woman/girl without conforming to sexist stereotypes. If they say anything to her it's perfectly reasonable for her to say "stop being so sexist. I can wear whatever I want, nothing stops me being female". If they don't say anything to her she can't do much. Sadly you can't stop sexists from being sexist.

It's harder to tell before, or in early puberty. DS was still mistaken for a girl after his voice broke at 14 (until he spoke) but not once he started shaving at 16.

If she's not asked, I'd say just get on with using the loo. It's not personal, just a sign of the times. I suppose she could pull out a packet of tampons etc from her bag whilst going into the cubicle if she wants to make a point. If asked, she could simply say 'im a girl, born and bred. I just prefer having short hair'. She shouldn't change her appearance.

When I say it will stop happening as she gets older, I don't mean because she will necessarily fill out - it's just that a female face becomes far more obvious as you get older. Of course it's confusing for early teens and they are often self-conscious but she'll get more self confident and it will stop becoming an issue.

DS has long hair and was mistaken for a girl when younger. Never when using the urinals though.

I work in a rural school in East Anglia. Lots of people ask about pronouns! It's definitely a thing.

My DD is 17 and for most of her younger teens, shaved her head and wore androgynous clothes. She got this a lot, as well as questions about pronouns. She just says "I'm a woman". It happens less now as she's a bit older and scans obviously as the woman she is.

She does NOT need to do a little something like wearing pretty earrings or mascara. Thankfully, DD was spectacularly not bothered by people asking and just shrugged off the confusion.

she obviously like having her hair short as that is quite unusual for a girl of that age, that’s the obvious reason she’s being misgendered. The easiest thing to do would be to grow it out.
Or just laugh about how ridiculous it is that as soon as a female has short hair all this nonsense comes up!!

It’s bonkers. My dd2 loves her short bob but says she needs long hair or people assume she’s trans or NB! She’s in year 8. I feel the world has taken a massive step back with stereotyping.