Sasha’s Fantasy of Adulthood
Sasha brings Anne to Toad Tower and immediately takes her on a tour of the premises, proudly displaying her extravagant-by-Frog-Valley-standards wealth and letting Anne partake in its comforts.
She's thrown around her wealth for Anne's benefit before, threatening to disinvite Maggie from her pool party (120).
And then there's that time she commits a coup.
Incredibly, Sasha expects Anne and Marcy to not only roll over in defeat, but to rule by her side (220). Although she was previously making progress toward a less controlling outlook (219b), she's utterly shocked that Anne responds to the coup by forsaking their friendship (220). I'm guessing that this warped view of reality comes not just from a desire for control, but from some more deeply held belief.
Being a Lieutenant in the Toad Army is a lot of work, but totally rewarding. I get whatever I want, whenever I want. […] I don't have to take sass from anyone or anything. ("My Dope Life As A Battle Queen!")
Sasha doesn't just want to protect, but to provide. Her fantasy of adulthood—Strength tempered with persistence—is that of a breadwinner. She wants to work hard, bring home the bacon, and be rewarded with unconditional obedience and adoration. Accordingly, she expects Anne to be swept off her feet by all the riches of the Tower, and for Anne and Marcy to fall in line once she sits upon a throne.
While breadwinning might have begun as a long-term control tactic (it's harder to leave someone you're financially dependent on), I don't think it's only about control—not anymore, at least. It's become entangled with Sasha's sense of self and self-worth, and it takes Anne's rejection to finally disrupt it.
Credit and thanks to @lapisinfrogjail for introducing me to this idea and much of the evidence.