My 2 cents worth.

If your girl has account at PNB then this works out at around 6 sterling so no doubt cheaper than that from the usa. It is alsoo possible for the money to be paid in $ rather than pesos according to the remit forms. It is possible to do the transaction online using cirrus/maestro card but still takes around 5 working days compared with 12 days if sending pnb a cheque ( quoting from my uk experience. WU looks to be very similar in charges to Moneygram which is available here and funds can be transferred and received same day provided transaction done at start of the business day because of time difference ( +7/+8 hours ).
Another means of transferring cash safe is Forexworld and last time I looked there was a set $15/$17 dollar fee regardless of the amount. Delivery is usually next day in cash delivered to your girls address, the money being taken from mastercard/visa BUT NOT AS A CASH ADVANCE so no interest charges to worry about. I think the site is www.forexworld.com and if not I am sure a web search would easily find it. Like Jeff says an atm card on your local bank is the ideal way but other than giving her the card next trip then these remain the main options.