Loose bowels in pigs is bad news 
but until you know one way or t'other (and it may well be that she'll slip off quietly within hours) you'll need to syringe feed her .
They don't like it . They will either fight or you'll feel cruel putting them through it but if they don't eat their guts go into stasis and they will get organ failure . Often they aren't saveable but give it a go.
If you don't have Critical Care mash up a few pellets and warm water until really sloppy and fill the syringe .
You need to hold the piggie securely (either towel wrap or place on your lap with the rump towards you and hold the muzzle in one hand )
You need the syringe just behind the front teeth and squirt a tiny bit , size of a pea . They need to chew , they'll chew the syringe . Then you know its going into the oesophagus not the windpipe .
Takes ages and you need to do every 2-3 hours .
If you have Vit C , give them some in water , same way .
Has she eaten anything like lettuce that has upset her ? Or too much fruit?
We lost our huge young boar to this -we did all the extra hay , cut out salad veg things . He went to the vet , they said increase his veg slowly , he improved a bit . Then a couple of days later , it came back with a vengance . He had saline injected , antibiotics . It didn't save him . The Rescue I got him from said they'd had a pig with the same .
The other pigs didn't have it so don't think it was contagious .
Though I did read later that vermin mouse pee can cause an infection in pigs that causes loose bowels !
Keep her comfy and quiet , maybe keep her in chatting range of her cagemate .
She might appreciate a very brief bumdip if her backend gets dirty save her skin getting sore .
Give her a fleece and some hay to sleep in.
Hope for the best , prepare for the worst .
Piggies are such fragile little things