I don't think stall is helpful in this battle, as any boosting move she uses (swords dance, bulk-up, calm mind) is boosted even more. One way to counter this is to get yourself a booster as well. Another way is to bring bulky psychic types (grumpig/musharna, who even uninvested have natural bulk and can withstand hits) as the boost in those moves help a lot and you can dodge ohkos from her sucker punches etc. Some flying/fairy types can be useful too (insert granbull with intimidate here and butterfree/vivillon with speed+ status moves).