Instead of see-saw, why didn't your hands to about the length of the bit and use 20% hand, and 80% leg, because once she puts her head down yes release for a stride but do not drop your hands, always keep them up. Once her head is down you still need to add twice as much leg. Always more leg than hand, always even pressure on both sides of the bit!
going off of Jayde's comment, try a soft bit like a lozenge or french link with no pinching. Everything comes from behind and the front end follows. It will take patience and time but teach your horse how you want her head held. See sawing or using gadgets like martinales or draw reins are only temporary and will not help in the long wrong.
No offence to your trainer but if she or he is telling you to see saw on your horses mouth you going to have lots of problems down the track and your horse is going to get a hard mouth and is going to be in alot of pain and we all love our horses and dont want that to happen. Make sure you are using a soft bit for example a snaffle 😊