This wretched bloody weather, I am so sorry for you
For me the best thing would be to lure her away from the site of the carnage and let her dry off, make sure she's out of the sight & earshot of the other mother and piglets. She will dry up in 3 or 4 days, take her feed back to her normal ration prior to farrowing, access to water. Her udder will be full and painful for a few days so push a couple of 400mg ibruprofen (ketofen is usual for animals but same stuff basically) in a banana or tomato and administer for pain for a couple of feeds. She will be vociferous and restless for a few days but generally they get over it fairly quickly, after she's dried up she'll come back into season and you could put her back in with the boar to occupy her mind.
I wouldn't try to foster other piglets on her it won't work in this case.
How old were the piglets? if they were only a couple of weeks old then I would make a huge really hot bonfire and burn them, however if they're bigger and older you may have to call the fallen stock people out to collect them. This is such a sad thing but get cleared up as quick as you can because of foxes etc, you don't want them tempted to your other piglets.
HTH
All the best
mandy