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First, check for physical reasons for her behaviors. Have you had her tack fitted recently? Call the vet out and have them do a thorough exam to find out if anything is wrong. Get a chiropractic adjustment to rule out pain as a cause for the aggression. If she is friendly and well-mannered on the ground, but shows extreme behaviors undersaddle, there is a high likelihood that it is pain-related. A poorly fitting saddle can create major pressure points on a horse's back and cause extreme amounts of pain. A horse that needs a chiropractic adjustment or is "out" may find certain maneuvers or being ridden in general uncomfortable or painful. Chiropractic in horses is becoming more widely accepted as people are seeing the very REAL results that it produces. Be careful though, and make sure you find someone who is credentialed and comes with recommendations. Many states do not require licensure of equine chiropractors, so you get some frauds out there who can mess your horse up more than fix them. Ask around, find out who other people in your area use.

Once you've ruled out pain, I think it's time to send her to a professional trainer. If you're too afraid of her to handle her and work through these issues, you're not going to be able to be assertive enough to push her past her misbehaviors. When you're scared or a horse that is displaying aggressive and dangerous behaviors, you put yourself in a very dangerous situation for both yourself and the horse. They need to be able to look toward you as the confident leader, and they sense that you are frightened, their behavior will only escalate.

But honestly, from what you described, I'm thinking that pain is most likely a factor. If you don't know much about saddle fitting, find someone in your area who does. An improperly fitting saddle can change a horse's attitude night and day.

The biggest thing is that you need to make her understand that those behaviors are unacceptable. If she pins her ears or snakes her neck at you and you step back or shy away, she just won that dominance battle. If you go out to catch her and she displays dominant or aggressive behavior, chase her away and make her run for a few minutes. I don't know how "easy" she normally is to catch, but after a few minutes of running, allow her another chance to come in. If she behaves herself, then she can come in and do something nice for her. Give her a treat, a good grooming, whatever, but make it a pleasant experience. If she's nasty again, chase her away and make her run. And I don't mean her her trot away from you and then stop to graze for a minute, get her RUNNING and keep her running. The point is to make her tired so that she doesn't want to have to run anymore. If she strikes at you or snakes her head at you like she wants to bite, try not to step away, but instead push back. Throw the halter at her, yell, whatever. Keep yourself safe, of course, it is better to give a little bit of ground than to be hit by a flying hoof, but then immediately drive her away, making it very clear that you are in charge, not her.

I still think that if she intimidates you as much as you are saying here, that having a pro come in for a few weeks and work through the hardest part would be your best bet. After they've established themselves as leader, they should be able to help walk you through the same steps yourself, and show you how to assert yourself as dominant.

The biggest key with horses that have that dominant streak is that once you have their respect, you have to work to keep it every second of every day. You cannot give these horses an inch. That doesn't mean you need to be beating them all of the time, or that you can't have fun with them. On the contrary, I've had great relationships with horses after we've established the pecking order, but the slightest deviation outside of the boundaries you've set, such as walking through you when they're being lead even ONE STEP, results in immediate consequences. You need to KNOW what your boundaries are, and what your expectations are, and then accept nothing less. There need to be quick and definite consequences when they deviate from the rules. You cannot be afraid to get a little physical with them, and give them a good smack if they need it. Horses are large, resilient creatures. A flat-handed slap on the neck or the rump is probably going to sting your hand more than them, but the fact that you hit them and the sound of the slap is what's affective. Sometimes the threat of being hit is also affective. Just like you'll see horses kick at each other in the pasture and "miss". A horse's hooves go exactly where they want them to, if they want to make contact, 90% of the time, they will. When they miss, they're saying "I could hit you, this is your warning. Shape up."
Also understand that a "small" behavior is never small when you have a dominant horse. Pawing quickly turns to striking. Rubbing with the head quickly turns to knocking you over, playing with the lips becomes biting, allowing them to walk even a half-step in front of you becomes running you over and dragging you, etc.

If she's whip shy, you can still assert dominance. I actually very rarely use a whip for respect work. I prefer the end of a lead rope, the nice rope ones with a little weight to them and a leather popper at the end (the ones that are popular in the natural horsemanship world) are my favorite. If you need to get your horse's attention, a pop with the end of the rope will create a nice "pop" sound against their hide and earn you their focus. If they walk over you while you're leading them, turn around and back them up fast, using the lead rope against their chest and demanding them to yield to your space as you come towards them. Sometimes you have to be a little "mean" at first to get their attention, to say "hey, things are going to have to change around here."