Hello jane take your pick,
hormones
lack of confidence at school and in the big wide world (so picks easy targets at home like mum and DBro for bigging herself up)
hormones
self consciousness (public displays of affection with parents or little brother, yuk)
getting too big for her boots
did I mention hormones?!
I am sure you keep calm but try not to raise your voice however infuriating, sometimes teens are spoiling for fight so any excuse to roar and they will.
Consequences like you've demonstrated, stopping pocket money or being grounded for a weekend when there's a party or trip planned so you become the meanest mum in the world. Winding up her brother or cheeking parents, needs nipping in the bud. You can have selective deafness if it's low level grumbling.
Don't forget some teens love to moan, "oh my mum's the worst, guess what she said last night", mimics voice, whinge, complain. But they will learn what pushes your buttons and if you are reasonable, she'll respect you.
Oh and you are bound to be slagged off on Facebook or whatever your daughter's on, don't forget thanks to texts every one of their pals is more up to date with her life than you or Dh.
The funny thing is they often relish parameters being set - you are a constant presence and all around them things can get chaotic: their peers are starting to outgrow old friendships, the opposite sex is suddenly a major factor and teachers are on about exams... Now they're halfway through secondary school and suddenly grown up life-after-school is beginning to sound real.
I found that taking a deep breath and letting DD keep her bedroom as she wanted it, not quite at bio-hazard level, was an important sanctuary for her.
The occasional treat - not to win her over or score brownie points, she'll see through that, more as a useful bribe - some item she'd like to wear, something like tickets for some event.
Carefully measured freedom in small doses, but trust has to be gained and any failure in contact, timekeeping or sobriety earns forfeits.
Sorry for the essay!