I'm more worried about the fact she has been quiet....but you say she has livened up a bit now.
I have had a few occasions now where yellow poos have been produced. In most cases, the piggies had quite recently been on banana-flavoured septrin antibiotic..(but many years ago when I was a kid I remember that the only time i fed fresh banana to my piggie he too got yellow poos as a result and scared the living daylights out of me- NB my current tribe won;t touch fresh banana)
All were fine and back to normal colour once they got some goood quality grass/spinach/dandelions down their necks...
So I'm going to hazard a guess that it's either
a) something she's eaten in the last 72 hours..(possibly banana or some type of coloured dried food?)...or
b) a lack of leafy greens such as spinach/kale/lambs lettuce/spring greens/dandelions/grass. (which is not unusual given our current climactic conditions

. state of the nation;s veg etc ec).
If her poo doesn;t go back to normal shape/consistency/frequency in the next 24 hours after a good feed of leafy greens then I would see a vet
Keep a close eye for wee/poo output and food/water intake...and it might be adviseable to weigh her each day for a few days to check she isn;t steadily losing weight as that is a first indication that there is something wrong.
Hopefully things will be back to normal by tomorrow....any cause for concern then suggest you see a vet sooner rather than later in view of the weekend coming up.
HTH
x