65/35 in Luigi's favor IMO.
Jiggly prefers to stay in the air.... well, that is a big problem for her.
Thing is, Luigi is also quite floaty, and he can spam 3 aerials outta one full hop. He is better than Mario in this MU because Mario's aerials and not-floaty attitude prevents him from fighting Jiggly in the air. Luigi can put up a fight in the air while Mario can't. His aerial mobility isn't an issue due to Jiggly will always aim for him when he is in the air. Plus, get caught in that Cyclone and you'll hate it big time.
Why Luigi wins this matchup because his recovery is HARD to gimp, and it travels great distance when pulled off properly. Plus, his ground combat is just as great as Mario. Jiggly prefers to stay in the air, Luigi Cyclone cannot be dodged as easily there, too. The only way to actually punish the Cyclone is with shielding, but you cannot shield in the air, and it's completely unreasonable to stay grounded just to block the Cyclone.
His Fireballs float, which can makes it a bit hard for Jiggly. Luigi Cyclone is an important thing to mind, as it can fight Jiggly's aerials. Plus, his B-air is a smash atttack in the air, and it hits HARD.
Luigi doesn't need his SJP other than recovering here, as Jiggly will stay in the air for most part. However, if Jiggly messes up her Rest..... well, get ready for a 'PWAAAANG!'. Although for most part, he will use his U-smash, and that move is crazy fast.
Oh, and you cannot crouch below the Cyclone I think. He sweeps the ground, and Cyclone's ground mobility is pretty absurd.
So yeah, I don't think Jiggly wins this MU, as Luigi himself is an aerial fighter as well. Plus, I think his aerials outranges Jiggly's.
So yeah, I'd say 65/35 in Luigi's favor, or 60/40 if you want.