It's funny how women in their 40's are criticized and called old yet them bitches is still in their prime. Keep on killin' it ladies you're an inspiration to us young girls - statement meaning

This statement is expressing a sentiment of admiration and support for women in their 40s. The speaker is criticizing the societal tendency to label women of this age as "old", implying that they are past their prime or less valuable. However, the speaker disagrees with this notion, stating that these women are still in their prime - meaning they are still strong, capable, and at their best. The speaker encourages these women to continue being themselves and "killin' it", or doing well in whatever they are doing. The speaker also mentions that these women are an inspiration to younger girls, suggesting that their strength and resilience in the face of societal criticism is admirable and something to aspire to.