I have an engagement to prepare for, and my cousin is sticking her nose into everything. She says weird things like, “That dress looks too simple,” and “Put on the gold set.” Honestly, our budget is fixed, and I don’t really care that much, but she seems to be constantly trying to put me down. Do you think I should just tell her directly and risk breaking her heart, or should I find another way to set my boundaries?
Does your cousin always act like this, or is he getting too involved in the engagement thing? And he’s also saying things like “let’s not embarrass ourselves” openly — is he saying it outright or is he implying it?
I mean, you say you have a set budget, but your cousin is giving you suggestions too; do you really have to look for bad intentions? Maybe they genuinely want you to pay attention, who knows, you could try to have a more constructive perspective 
I think your cousin might have a point. After all, an engagement is meant to honor your family’s reputation. You mentioned something about a gold set, and guests always pay attention to these details. I know from my own wedding, people talk 
It’s your friend’s engagement, why bother worrying about what others say? The friend above said something like “people will talk”; what kind of mentality is that? Just wear what you want, why do it according to what others think?
And you know how they say that if you wear a cheap dress at the engagement, it brings bad luck in marriage. That’s why your cousin might be a bit hung up on it. Although I’m not sure how true it is, I’ve heard it from the older folks 
I completely understand how it feels when you hear those “it’s just simple” remarks. Especially at a moment when you’re considering the budget, it makes you feel like they disapprove of your intentions. I think if you calmly but clearly say, “this is my budget, and I’m happy with it,” it would be reassuring.
Let me add that my relationship with my cousin has been alright since childhood, but his constant meddling is really stressing me out. I wouldn’t mind if he just said a couple of things, but he’s always talking. He’s literally non-stop.
You literally said “you’re not listening,” but why don’t you just clearly tell your cousin “don’t interfere” then? If things were going your way, you wouldn’t have spread this all over here. You’re putting up with it by saying “but we get along well.”
Childhood friendship is such a difficult bond… One makes sacrifices in everything to avoid hurting the other. But right now, it’s one of the most special days of your life, and this is your moment, really. I think it would be enough just to make him feel that.