To be annoyed at colleague for doing too much work?

Don't worry about her and carry on with your own work style. If she's so quick she may make mistakes or not come to the same conclusions as you, having given it more time and due to your greater experience.

I'm definitely a tortoise not a hare and if I go faster I tend to make more mistakes.

So you want her to work below her level of optimisation to make you feel better? Come on, OP.

It's not her job to allay your feelings of inadequacy. You either step up or you just accept that she's one of those very efficient and capable people in life.

As a PP said above – I am also incredibly efficient at work. I can fit the same work into half the hours as my colleague and perform the same, if not better. That's not necessarily a brag; it's just something I'm good at (and there are many other things I'm not good at it life!). I would not stop the way I work for anyone.

Yabu.

You are responsible for your feelings of inadequacy, not her. Why should she dim herself to make you feel better?

She may like and enjoy her job, wants to do well, keep it, and progress further.

Being quick is my USP and main work skill, and I’ve built a successful career and reputation on that.

Same here. If someone came to me and told me to lessen myself unnecessarily, I would ignore them, maybe even go harder.

I get why you're feeling how you feel, totally valid. But you can't ask her to slow down, you'll just look bitter - and will draw attention to you working slower.
Is your pace OK? Is your boss happy with your work? If she was just working her hours would she be so far ahead?

The only thing I would perhaps mention is the risk of burn out working out of hours/on leave. It would piss me off too, and depending on how well you get on with the boss I would maybe have a word out how you're feeling. Something along the lines of you feeling you're falling behind as you can't dedicate your free time and annual leave to work activities. I wouldn't want to work in an organisation that promoted or rewarded that.

But unless you're her manager, it's not your role to pull her up on it. Don't tread on your bosses toes.

I don’t think you are unreasonable, by the way if you’d put that without her age everybody would agree that she was wrong to use her leave for work. As you’ve mentioned the age it looks like you are envious as she is young and quick but it’s not this. She’s got advantage by using a leave. Was it intentional or not but it did made you look less adequate and less committed.
It’s a bit like one of your colleagues sending a long email on Saturday morning. And by Monday morning everyone replied except you as you’re the only one in the team with small children. It sucks but nothing you can do about it.

She's working on her free time, which sets an unreasonable bar to everyone (no one who works the normal hours will be able to keep up with her).

However, I think it's not up to you to say that. In some workplaces her behaviour will be taken into account (and treated as the exception). In others, you will all be compared to her. There's nothing you can do.

(I used to be like her. Then I had kids and my career went kaput)

Absolutely YABU. Being quick is my USP and main work skill, and I’ve built a successful career and reputation on that. If someone asked me to slow down, I’d probably nod politely and then carry on as I was building and progressing in my own career.

She shouldn’t be working while she’s off really, that’s a bad habit to fall into.
Apart from that I think you know YABU, she has put your nose out of joint. You have to either change it up a gear at least while you’re working together or accept she is going to look a bit better than you on this project.

Why does the meeting prep matter? Providing you have time before the meeting to prepare how you usually would, I don't see the problem. She's just done it early. Also, a lengthy summary document sounds tedious so possibly she is wasting her time. Might be better to just chat things through at the meeting based on your experience.
She sounds keen though. Which is a good thing!

She's young and keen, more fool her for working when on leave.

She will eventually become old and cynical like the rest of us.

Wow. Of course you can’t ask her to slow down as she’s making you look bad. Step up yourself!

My boss would pull her up on working when she is on leave, and I think she is right too. She is quite strict about people not building up ridiculous amounts of flexi, or working when they are meant to be off work. I do think being a good manager means you don't let people build up these habits that can lead to burn out. It can also creates a toxic culture in the team if other people start to feel pressurised to work out of hours.

So for that bit YANBU.

Well I understand your feelings and if I were you I would feel I definitely have to do some prep and thinking before that meeting. Good that she is keen, but more experienced people.know that this might be wasted effort if it's a group decision on how to proceed.

You're just bitter. You can't tell someone to not be themselves, she's obviously trying to make an impression and better herself.

Yabu. She works how she works. You can’t ask her to slow down to make you look better.

You can ask her to stop sharing her thoughts/findings/answers with you.

But asking her to not be as on the ball because of your feelings is unreasonable.

I think all of that

Id find it annoying but she's young, keen and good.

Maybe she'll calm down a bit, or be given more to do.

You are being unreasonable. She sounds brilliant.a little bit of jealousy maybe (understandable!).