Amber has been patiently waiting for Becky's mental health to decline. She knew Becky was vulnerable from the start. The goal was easily attainable - Amber just needed to keep showing Becky the negative comments about her on YT/YN/KF and give her random subtle jabs ("I don't think girls with round faces should have short hair"). Lather, rinse, repeat, and wait for Becks to get more and more depressed.
Once that was done, Amber could begin to instill her own defeatist attitude onto her partner. "See babe? They only hate us because we're fat, no matter what we do they'll never love us. Let's drive 2 hours to the nearest Cheesecake Factory to prove to them that we don't care what they think."
Remember when Amber "pranked" Becky by saying she wanted to just give up and wait to hit 600 elbees to get on the TV show? That was definitely a test - a barometer reading of sorts - to see where Becky's attitude was. Becky immediately responded with "no, that's stupid, you're going to die" so Amber said it was a prank. I think we've finally reached the point where Becky's depression has caused her to roll over. Yes, Amber. Sure, Amber. Whatever, Amber. Let's just eat our feelings to insulate ourselves from ever feeling like we need to improve. I won't tell anyone you can't fit in the front seat anymore in exchange for more Hot Topic credit.
Amber's decline in content will catapult them back into poverty, and her IDGAF eating habits will glue her to Pillow Mountain. Buckle up, folks.