AIBU to feel hurt my cousin hid booking her long hoped for trip?

Something similar happened me before, I imagine what happened is that you well-meaningly suggested a specific way to do the trip, or destinations/tours to include and she didnt book it as she didnt consider it as interesting as you did and is worried about insulting your taste, OR couldn't afford to do all the suggested things and didnt want to admit it after you giving all your helpful advice. Some people slways expect others to take offence and act sheepish before offence is ever taken! The only way to deal with that is to say "I hear you booked the trip!! It'll be amazing, be sure to ask if you think I could be useful for tips etc" and change the topic completely.

Except, the OP would be telling her she'll have a fantastic time, again, as though she knows more than the cousin.
My older sister has a habit of speaking to us as though she is the oracle on all things. Yes, she's travelled more than us, but she's a completely different person and we don't want her input, to the extent she wants to give it, or ongoing opinion.
OP, really think about what your reaction has been when she has said she's going to do something you've done. My middle DD has really had to kick back and remind my eldest that she is now a full adult. Perhaps you piss on her chips a bit? You might have slipped into older sister mode, but because you aren't a older sister, you now just want to cut her off, because she isn't dancing to your tune. Do you enjoy playing saviour? Before you contact her, think what you want your relationship to be, don't let her dump on you, she has a Mum and start again with what you want. Acknowledge her booking the holiday. Siblings sometimes have to reevaluate relationships, as they go into full adulthood.

I would just casually message her and say something like. “I’ve just heard about your trip from your mum. It sounds fantastic. I am so happy for you. You will have such a fantastic time and I can’t wait to hear about it. Lots of love xx”

Whatever happened to communication?? Just tell her you know and that you're happy for her. No need to be nasty about it, just be plain and open. For heaven sake, has the world gone crazy?

She's not being needy, just being perfectly reasonable wondering why her cousin is being weirdly evasive

And yet it’s within your power to change.

Let the woman live her life as she wishes.
Stop this needy behaviour @Asvan .

Are you feeling a bit like a foul weather friend Op? Always there for support but never get to share her good news, I can understand why you'd be a bit miffed

Agree. People say some wierd shit on here!

Being so deeply upset because someone hasn't told you they've booked a holiday is way too much.

I avoid talking about holidays with people who have been to the same place because I like to just discover things for myself and rarely want all the insight people feel compelled to share.

Quite understandably, IMO. I'd withdraw a bit now, @Asvan

You feel used because she does use you. You are her sounding board, the one who buys her coffees and commiserates over her hard life. She doesn’t want the narrative to change.

You really need to think about what you are getting out of this.

She is looking forward to her own experience. and you being overly invested or talking about your own holidays will take from that.

You can feel however you choose, but she’s not obliged to share everything with you.

Can you text her and say something like “ Hi! Your mum told me about your trip to X. Sounds fantastic! I’m so glad you’re getting your dream
holiday. Speak soon”
Absolutely don’t go down the road of ‘ooo you never told me’
i had similar experiences with a friend a few years ago but I won’t bore you with the story.

Does she buggery sound needy 🙄

It's the fact that she's avoiding her. Wierd of her cousin to suddenly distance herself. I'd simply be asking her if everything was ok...

So stop being the person on whom she leans in bad times. That’s your choice, to listen to her sorrows and complaints, lend her things, pay for her coffees. Those things are your free choice. No one has you at gunpoint. If you don’t want to do them, stop. If you feel exploited, stop. What you don’t get to do is to do those things resentfully, and then expect certain behaviours from her in return, like the disclosure of certain information you feel you’re ‘owed’.

Is it Haj?
She may have booked the cheapest options and is embarrassed to discuss it with you.
Or wants to just go with her mum rather than you tagging along.

Yes, exactly.

This relationship sounds far too enmeshed for its own good, and I feel there's an imbalance to it somewhere. You obviously feel that you've invested heavily in it and you view the non-sharing of all or any information as a lack of "return" on that investment. That's not healthy for either of you.

If I were your cousin the two most likely reasons I might avoid you after booking are:

• you might try to come along too and I don't want you to
• you might tell me I am doing it wrong somehow and should do it differently

Could either of these be the case for you two?

I think you are a little over-invested in her life and in the relationship. Why is this bothering you so much? Maybe you need to take a step back?