In answer to your question of what's wrong with the scene: there are spelling mistakes, mixed tenses, plus punctuation and grammatical errors. It doesn't flow.

Hi Erma,

Welcome, it is so nice to have you here among other Authors. Have you finished your next book, and what is it about?  I write self-help guide books and will have my first 2 books published soon(my first book will be re-published) I have finished my third book, and now working on my forth, I will have 6 series in all. if you would like to learn more about me and my books you can visit my website www.wix.com/LisaBrereton/itswheretheheartis  then just click on my blog. I would love to learn more about what you write Please stay in touch

Lisa

Here is my re-write with the hopes it may be interesting to you:

Liza fell off her saddle hitting the defrosting ground with a loud thump. She Rolled until she hit the stack of rocks that would protect her from the bullets.

Gunshots were peppering the ground and the tall saw grass that waved in the afternoon breeze was her only protection. She grimaced in pain as her hand brushed her side. She looked down at her palm it was bloody. She wanted curse like the cowboys did when they were shot, but what good would it do in this fight for her life?

The sound of her horse disappearing over the hill wanting safety from the noisy gunfire that continued to hit the ground near Liza. Liza crawled through the grass near sagebrush, trying hard not to make anything move and give away where she was.