Explaining to Mom
Trixa, Your fundamental problem appears to be one between yourself and your mum. It is not as uncommon as you might think, my own Mother never really understood me. Somehow you have to get across to Mom that you do not have the confidence to ride but now you really want to find a way so that you can enjoy the horse she bought for you. She is going to offer to help you because she believes she knows how, but what she won’t accept is that she can’t teach you - she simply doesn’t have the skills to teach a complete novice.
For all sorts of reasons you need a professional trainer - which your mum thinks is a waste of money.
To give an example - I have always felt comfortable in water. The trick is all about relaxing. “Go with the flow”. But I have always had a problem trying to show learners how to swim. I simply can’t understand why they have phobias of being in water, certainly fear of water is something which I have never experienced. Likewise your mum simply can’t understand your fear of being on horseback. If a horse bolted with her on its back, then she would be seriously annoyed with the horse, not frightened of falling off it.
When my brother wanted to learn to swim we were holidaying in a hotel with a pool which we had all to ourselves. Luckily the pool had a shallow and a deep end. Over the course of a few days I showed him that if he closed his mouth and held his breath and jumped into the deep end that he couldn’t sink. He would float with his feet down and his head above water; the air in his chest would act as a buoyancy aid. To his credit he did as was told and he floated with his eyes above water. Then all he had to do then was to work out how to move in water, so we did the dog paddle together. Now dog paddling isn’t either the most effective way to swim nor the most elegant - but it works and that’s why dogs do it that way. Eventually my brother learned to swim properly. The big problem had always been to get him to try.
If, as a novice, you’ve been on a horse which has bolted off with you, then somehow you must erase that memory of being out of control. Your new 3yo will not be the horse to erase your fears. You need a calm school horse and you will need to progress, taking one step at a time. You also need to understand the theory of riding and I doubt if Mom has ever bothered to worry about ‘boring’ theory.
So my suggestion would be, go find an instructor. Go say: “hello“. Explain your predicament and then go home and tell Mom that you really do want lessons so that you can learn to ride like she does. It is worth a try.
PS Always wear a riding hat - whatever Mom says.