Bullying or the boar hurting her were my first thoughts too. But it could be any number of things
I'd get her in, on her own, as soon as possible.
Check temperatures and feel all over her body (sore areas, especially in the legs will feel hot & you'll know if it's causing her pain
) You'll also be able to check her poo - it could be that she's constipated, but unless you manage to catch her having a poo in the field it'll be impossible to tell. When it's wet & muddy pigs will often avoid going to the drinkers (cos round the 'feeding station' is usually worst affected) so constipation could be a possibility.
She might just need a couple of days peace from all the big ones, or she might need treatment of some sort.
Get her in first and come back once you've checked her over
HTH
Karen x