Sounds like u defo need a different mon to take it on. Ice types are good against her whole team, especially if they know ice shard or are just fast enough to outspeed some of her team. Beartic is pretty slow unfort and would probably die to Hyper voice like you said. When I took her on in my last playthrough I had a Sturdy Golem and Weak Armour Vanilluxe, at levels 70ish (cant remember exactly), if you wanted to try either of those, you can catch their pre-evolutions around the mountain close by, but I don't think you can avoid putting in the effort to train another mon, sorry.