Ow!
Hoof abcess? (aka gravel) or in her leg? Not that it makes much difference: they both cause unbelievable "I've-broken-my-leg" lameness.
My Cleveland Bay has had gravel 3 times in 9 years. It often seems to come on when it rains after a prolonged dry spell: apparently the dry shrinks the hoof and the wet then means dirt and infection can get drawn up the white line. Once the pus breaks out, the lameness reduces to a slight hobble. Same with a leg abcess. I keep a close eye on his hooves these days: if you catch it soon enough you can prevent lameness.
Re laminitis: my pony suffered from it once years ago - I still have no idea why - but the classic stance DID come on overnight. She had, in retrospect, however, been very low and off for a couple of weeks beforehand. Her legs were a little puffy, not surprisingly as it is an inflamation, but not hugely noticeable. What was obvious and I'm told is what to watch for, was the hard thumping pulse in her pasterns!
She's only ever had it the once in the 27 years I've owned her.