To be fair, most succubae will not want to be caught flying, or exercising, ruins their image (well, most).
Gliding is something else entirely, but you need a good bit of starting altitude/velocity and/or heat currents from some strategically prepositioned heat sources to pull it off, and if you're using magic why not just levitate?
Izah is more likely to use a parachute. The corporate kind. Why fly when you can pay someone to fly you?
Ah, I believe you may be confusing Abyssal media for the tomes of demonologists.
Within the Abyss, female demons are acutely aware of the lengths that the top figures in the Abyss go to maintain their figures, and the journals are full of paparazzi sketches of one powerful demoness or another working out in a sports bra by jogging, flying, or fighting slaves in their personal gladiatorial arenas. After all, it's only
poor, lower-class demons who are Gluttonous these days (though things were different in the past) and these days Lust, Pride and Envy are in the ascendency and all of those demand personal perfection. Rich demons are the ones who can afford personal trainers and the like - it's a mark of conspicuous consumption. Sure, powerful demons will dress up impractically for formal events, but in day to day life you just wear something more practical, whether it's a leather apron when you're jabbing tormented souls with a pitchfork, or the black robe, white undershirt, and cravat of the practitioner of the Blackest Art.
By contrast, many demonologists are single men who avoid socialising with others and instead obsess over their imported books written in strange foreign runes, filled with lurid drawings of demonesses. Many of them get in big arguments with other demonologists about which summons is a better wife candidate, and express the sentiment that the other person's favourite is a terrible choice. They expect certain standards from their succubae - they have to look suitably pure and nothing can break that illusion of depravity, they need to dress in totally impractical outfits, and they often don't understand that the pictures in tomes of demonology are just drawings and artistic liberties are taken.
Izah'belya honestly finds business management much less stressful than the eighteen months she spent as a summons before university. It's much easier buying bulk orders of souls and employing others to do the dirty work than having to cater to the whims of some bespectacled demonologist who thinks because he taught himself the Black Tongue to read tomes he can actually speak it properly. Oh, sure, a few top succubae are mega-rich because of it, but the working conditions are exploitative even by the standards of the Abyss and your agent and your manager (and your mother) take most of your earnings. Life as a low-ranking demonic servant sucks, and most never get their big break.
