Developing a fear to ride.... Help?

I just bought my first horse on April 5th... It was a dream come true. I've always wanted to own a horse, and worked really hard to make this happen. I was really careful when I bought my horse. Or so I thought. I visited and rode her more than once before my purchase to make sure she was what I was looking for. She's a 17yr old POA mare. Suppose to be "deadbroke." The previous owner had her well trained, and she seemed really quiet, sweet, and had good manners. Well, it's another story now that she is home with me. She's starting a bad habit of bucking or rearing when I'm getting ready to dismount (or she thinks I'm getting ready). I usually get a split second notice before she throws me because she starts to make a very quiet "neigh," turns her head slightly to look at me, then.. I'm flying through the air. I haven't ridden her in a month because I'm afraid. On the ground she's half and half. One day she'll run to the gate happy to see me. Then the next she runs away like I'm the grim reaper. This really breaks my heart to become afraid of something I enjoyed so much. Has anyone gone through this? How did you overcome it?

1. I'm starting the Parelli's videos.
2. We've changed saddles and pads in case it was an issue of comfort.
3. She not "hot," she is getting no grain at the moment. She's getting on the puggy side from not being ridden.
4. I've spoken with the previous owner about my issues and she's is surprized as me with the change in personality. She seems honest.
5. I was taking lesson, but they are on hold due to Michigan's economy... Need I say more....

Sorry this was so wordy!

Sometimes, unethical sellers will "sedate" a horse when they are being looked at, and that very well may have happened. I hope it's not the case, but there's really no way to tell.

That being said, it may be worth it to have a trainer spend some time with her, and definitely worth it to continue your lessons. I know the economy is rough, but in the long run, I think it will be worth it. My husband just started taking them and his confidence is building tremendously.

Maybe there is a lesson/trainer place near you that you can ride your horse during the lessons?

ETA: Can you work out a "working student" plan at the barn you were taking lessons at to help pay for them? I did that in Maryland. I worked a few hours a week when I could mucking stalls and what not around the barn and got a massive discount on my lessons. Worth a shot to ask!

"Working Student?" That's a fantastic idea! It's a mom and pop boarding facility I use. I bet they'd go for that!

I would try lungeing her and working on the ground. Also, try to work with a trainer. Get her use to a saddle or weight, maybe she is in pain or has a medical or emotional issue.