Ungrateful cousin thinks I copy her?

So a couple months ago my cousin got an adorable golden retriever. I've wanted a dog for my entire life (I'm 13) but it was always an impossible occurence. Well my mum finally decided we should get a dog so I was so happy and told my cousin. She rolled her eyes amd said I "copied" her and I only want a dog cos she has one?! What?! Its so annoying because this happens with everything. Like she said I copied her for joining tennis and playing the game colour switch.
On top of that she is really ungrateful. She would rant to me about how her Mum isn't getting her the iPhone 8, she is "only" getting the iPhone 7 plus. Ugh. And I have my sister's old samsung flip phone which I pay for myself.
Also last year she got a some £500 pound ted baker bag which she complained about it!
She is also so clingy! She is in the same year and same class as me:\
She accuses me of being clingy and following her around when she's the one trying to hang out with my friends (who she hates) or spamming me if she sees I'm online. I was at her house and she wanted to have a sleepver and I explained that my sister was leaving for abroad university and I wanted to spend time withh her but she secretly went behind my back to my mum and convinced her to let me stay!
She's very moody. Like sometimes when i'm over, she sits on her phone all sulky.
I can't get rid of her! We're related and my Auntie loves her and won't believe me. Everyone thinks she is just some sweet angel:/ what do I do?

I don't know

You are more grounded, because your parents aren't buying you off.
Your cousin has low self esteem, because she has been brought up to think that possessions and new purchases somehow get you happiness- and clearly it isn't working that way for her. When she complains, it's her way of telling the world that.

Don't bring that up with her, just understand she isn't a happy kid. Perhaps you could share with her about your dogs, and ask her to join you at obedience class, or maybe take up agility or better yet, freestyle!

Never mind what anyone owns- challenge her to follow you in working with your dog and *achieving* something. She'll feel better, and the two of you could have a healthy rivalry going, something that could help you both. If you try and bond over the dogs, you could all be better off.

Don't ever mention the problem with having too many possessions and not enough self worth. Just show her how much fun it can be if you want what you have. It's a bigger gift than anything else she will ever get.

Talk to your parents about her