A wise horseman once said the best way to get a horse to lope slow is to lope them a lot.
Also, I would work on vertical flexion and softness so that she is encouraged to round her back and use her hindquarters more.
To teach her to "move into the bridle" is more than just holding onto her face. You have to teach her how to accept the bit pressure and be light. She should go into the bridle and yet weigh nothing in your hands. First teach her how to give at a stand still and then a walk and then a trot and then finally a lope.
What you want to do is take a rein in each hand and put a hand on each of your thighs. Don't try to smash her toungue, but just feel it. You want your inside rein a tad bit shorter so that she will arch in the correct direction and this also will help prevent her from bracing against the bit. Now you will massage with your inside hand, nothing fancy but little movements of your fingers or wrist. When you feel her weigh even a little bit less in your hands drop your reins. At first you will probably have to hold on for a long time until she figures it out, but eventually she will get quicker at softening. Be sure to do this in both directions.
Once she completely understands that when you take hold she should soften, then you can have her hold it for one second before you release, and then two and so on. Then you can do this during a walk, but this is more difficult because you will have to keep her moving forward with your legs. When you go to the walk start back at the immediate release and work your way up again to holding it for longer periods. The same applies to the trot and lope.
This is great for her to know because she will carry herself better, arch her back, and engage her hindquarters. Not only will she be smoother, but she will slow down as well. It's worked on all the horses I have tried it on, so I'm sure it will work for you.
If you have any questions I would be more than glad to answer them, this is one of my favourite subjects
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