S.A.
Speech errors are very hard to correct at home. I tried working with my oldest until I was blue in the face because her pediatrician told me to wait and see before I took for an evaluation. She made no improvement so she started therapy when she was four. I'll never forget when she came out of her very first session and could say her "s" sound. You could have your daughter evaluated and see what they say. If she needs therapy, it can do no harm.