It seems like Wbhotia's idea is the most constructive - a practical interview to see what skills she actually has. Pure "interviewing" is notoriously ineffective for many types of employee - everyone is on the their best behaviour. I have also found actually speaking to former employers to be also very useful - but you do have to be able to "read between the lines". If someone is hugely positive then that's fine, but if they say something like "she was OK" that normally means "OK on a good day but I don't want to say anything too bad" - so you have to ask good questions to find out sensible answers. Good luck with your next one.
As to probation periods, I suspect this is impractical given they come from overseas and have some fixed costs of getting here and home again. One month salary to pay to get rid of someone is not much, given the low level of the salary.