I know this post is a little old, but I had this problem before with getting my binders.
For a long time my mom viewed it as a really stupid item and refused to let me have one, and honestly it took a really long time, which probably isn't what you want to hear. It wasn't even that she was more open with me being trans, it was that she saw how much I hated my chest and it affected me. So I'd definitely start dropping those things, like mentioning that you dislike that part, and making it seem more apparent. Believe it or not, it really didn't give away to anyone I was trans.
Also yes, I'd say go through a friend. Make sure you size yourself right and in my opinion if you feel you have a smaller chest, maybe broader shoulders go with GC2B for sure! Also unless you want issues with it sliding I'd also go with a half tank. ESPECIALLY with Underworks which is better for people with larger chests.
Be careful with your binder and trust me, don't go smaller, if you think it'll help it wont. It just hurts.
Also as far as dysphoria, it can be a total bitch don't even get me started but I found working out really helped a lot in decreasing size and also just making me feel more confident. It buffed out my shoulders and really just helped.
Now thankfully I have a fully supportive mom and she bought me my binders, but it took time! So hang in there, YOU GOT THIS!
You have the power to say "This is not how my story will end".