E-mail seller asking if there is any problem with your postal order as they should'nt have to clear in the bank (check this with the post office first). Tell her you are waiting for your item and see what the response is - if nothing materialises then report her to e-bay.
What's her feedback like? If she has 100% chances are it;s something genuine, if it's less that 97. something perhaps something is a bit fishy!
Cannot understand a seller without paypal! Unless they have no bank account/card with which to set up the account?? Which could lead on to questions about there own financial arrangements, past bancruptcy ect ect??