Try 4-D mode
Though I think you should start trying out some different characters but I don't know if 4-D mode is the best place to do that
Freya ... the first place I defeated her was on Universe actually since I was more experienced at the game then. I never got to her on my very first playthrough of Galaxy because I gave up after Lenneth who back then seemed impossibly hard - I had Nel/Albel/Sophia and she kept on killing Nel and Albel V_V So I had Sophia running around the battlefield like crazy alternating between reviving and spamming Explosion. After what seemed like an eternity and I'd almost ran out of all my items Lenneth died to an Explosion that was still on the field whilst I was reviving Nel and Albel o_o I got the defeat Lenneth using Symbology trophy from that fight haha. She took all the fight out of me for that file though and I lost the heart to play it.
For Universe Freya I had an MP tanked Peppita with Cliff and Albel loaded with boots of prowess. Despite this only Peppita was really durable eating all Freya's attacks but Ether Strike whilst Freya regularly smacked the crap out of Albel and Cliff V_V I think it's because DEF isn't as effective on higher difficulty modes. Anyway I eventually won thanks to lots of powerful Faerie Friends from Peppita but she had to do a lot of reviving with items between times.
On that file I remember trying all sorts of strategies to try and get her time limit trophy from her but Albel kept dying and screwing it up. Eventually I got mad and stuck him in a corner on item duty for stunbomb and healing item use whilst I alterated control between Cliff and Peppita keeping Freya bounced between L/R Max Shockwaves from Cliff and S/R Power Dance > Faerie Friends from Peppita
Defeat Universe Freya in twenty minutes received yay.
SuperJolt - Hey no problem.
Your vids have helped me out a lot. I'm now juggle crazy thanks to you
The Loot Item strategy does indeed work pretty well - I have a thread about it at GameFAQs. I've been trying other juggle combos as well like Albel's anti air + Loot Item with Peppita's Charge and Adray's Aerial with Peppita's Charge.