From Leah's 2016 essay on Hypebae about her "love affair with my Bipolar II disorder":
"I turned a dark corner when my hypomania got out of control and became dangerous. It was so hard to see that I was out of control. I felt charming, seductive. I swear I even feel like during these elated times I look sexier and prettier. I was sexually insatiable, I spent a lot of money I didn’t have, and I was agitated and impulsive... it’s a constant hunger, a constant need for stimulation.. I thought it would be a great idea to go to Spain for a weekend even though I had just been there for two weeks not long before. I also thought it would be a great idea to change Kier’s school out of nowhere, buy a couch that cost $10,000 USD, and date a couple. I couldn’t sit still and I couldn’t stop spending money."
...That was in the summer of 2014. I have been in remission, as they call it, since then. After trial and error I am on the right medication cocktail. Sometimes I want to go off it all but my support network of friends and family always talk me out of it."
So when Leah is having an unmedicated episode, she engages in hyper-sexualized behaviour, acts impulsively, has no judgement, lacks any self awareness and is incapable of seeing she's completely out of control. The disorder also causes her to mistakenly believe she is actually more charming, prettier, and sexier when in a manic episode, or off her meds, or drinking.
Which pretty well describes Leah's behavior 70 percent of the time on the show.
Which means Ramona is...sorta right (the fuck? How did THAT happen, guys? The assurance that Ramona will always let us down - throw a glass, say something brutal, walk in a bikini and high heels with all the grace of a constipated pigeon in hot pursuit of a man making over 400K a year - the Moaner touchstones! - gone. Poof! Ramona is now the voice of reason. Ramona is now discussing best practice protocols, diving into non-engagement, and refusing to be baited into the fight Dorinda is trying to choreograph with all the wet-lipped passion Medley usually reserves for her roast chicken nights with Lenny Briscoe (speaking of juice). Welcome to the new decade: Covid. Murder hornets. UFOs. Killer seeds, And Ramoner the Reasoner. We are so screwed.)