she did very well not quite as good as the BM against all HM but that is a range issue.
Some of it is range issue, but also HM is
Blossom's specialty. Lvl 3 Blossom has +90% attack damage, but Buddy's HM attack bonus is only +60%.
Added more info: In two identical provinces #57 so the same map/terrain I had 5 Treants as enemies and 1 time was 5 Buddies sent to battle and the losses were 5-15% across 4 of the 5 but the next round I sent 5 BM and won with no losses. Maybe just the inherent range difference but without a doubt I took significantly less losses when using the BM over Buddie, but never a loss.
This one is definitely a range issue. Buddy's range is only 3 and a Swamp Monster's (enemy Treant) movement is 2 with an attack range of 1 (2+1=3). Therefore, to get a shot in, Buddy will have to put herself in position where she will now be in reach of a Swamp Monster (or Orc General) when it's his turn. In the Province 50s, there's no way she can take one out with only one shot. Therefore, the Swamp Monster will get a retaliation shot in, though hopefully nerfed at 50%. If you manual fight, you can still use Buddy on Heavy Melees with no damage if you are able to put an obstacle between them. On the other hand, Blossom's range is 5. She can hit a Heavy Melee, including Knights (his movement+range = 4, too short to reach 5), and still stay out of their range. Hence, you should
use Blossoms across 5 HMs. I generally deploy Buddies to buy me time against Heavy Range, especially if I have to take care of pesky enemy mages first.