The reality is (as has been posted a trillion times before) that you must be able to effectively communicate to be a good pharmacist. Of course the writing sample matters or they wouldn't have you do it... the adcom has enough reading to do with the thousands of personal statements and supplemental applications.
I am sure that they will take into consideration that english is not your parent language, however, it is unlikey that they will give you a free pass.
I suggest working on your writing and English skills as much as possible and think about taking a writing class... or applying to a school that does not use a writing sample.
I wish you the best of luck.