I have a 6-month-old girl. She keeps poking her own ears to the degree of bleeding a bit.
The only way I can think of is to trim and polish her finger nails often but is there any other way to prevent this from happening?
Trimming fingernails is obviously a way to prevent cutting and bleeding, but it is worth looking at why she may be sticking her fingers in her ears. It may be just a habit, in which case distraction techniques can work, but it could be an indication that she has pain or irritation in her ears and is trying to alleviate that. A quick visit to the doctor could have a check on ear irritation.
Six months old is too young to consistently redirect. And trimming her nails really doesn't solve the problem.
I'd start with her pediatrician.
Beyond that, I'd cover her hands with little mittens. Unless there is a medical issue, it will probably get better on its own within 6 months.