My DD is in a similar boat. Regular and even slim fit jeans are too baggy on her waist, and she can't stand how that feels (even with adjustable waist pants). At the same time, even regular fit jeans fit too snugly for her in her thighs for her liking.
And leggings? Too often they gape at the waist, too.
What's a girl to do? Her best luck with leggings so far is with Under Armor and Nike Pro. C9 at Target fits ok, too, though it seems not to hold up as well in the wash.
At school, if she wears leggings, jeggings, or yoga pants, her top is supposed to cover her tush. Finding clothing every day is a nightmare. She usually ends up in leggings or jeggings (and YES! Justice FTW!) under a sweatshirt. Occasionally she'll wear a tunic, but that's rare. They're too much like a dress and apparently, dresses are a super no.
She'll sometimes wear her Under Armor or Abercrombie sweatpants, but as a
middle schooler now, she doesn't wear them often anymore.
Sometimes though, we do also have luck finding jeggings at Target. And once in the bluest moon, she'll wear their Cherokee brand jeans (some are soft and spandex-y).
I've had days where I've seriously considered trying to open a clothing company to ensure DD has clothes that fit!
FWIW, DD is 11 and maybe just starting some of her growing.