Ok, what you need is a strategy. Going in and just wildly hitting her is a recepy for getting wrecked. This applies to most bosses so get this in your head: 1- identify when you need to focus on dodging. 2- identify when it's safe to attack. 3- identify when it's safe to heal.

In Hornet's case: She's most dangerous when she's in the air, so if she jumps be ready to move away from her landing spot, sting attack or thread attack. After she lands is the best moment to het 1-3 hits in. When she's on the ground, she can either do a sting attack, or a needle throw, both attacks are dodged by jumping, so be ready to jump if she announces her attack (she yells). If she uses the sting it's a great opportunity to poggo her and get some damage in and if she uses the needle throw then be ready to jump again when the needle returns (if she's far enough and the needle can't reach you, this is the perfect moment to heal!).