Under other circumstances (i.e. you and the girl have been dating for a few years, met each other's families, know each other's intimate details and true character through personal experience, etc.), then you might feel that a prenup is not necessary.
Granted that you've never met this girl, have doubts about her intentions - there are just too many red flags for you to ignore.
She argues that if I trust her like I say I do then it wouldn't be necessary but I've explained to her that I've seen people change their mentality and beliefs and a person could often like someone one minute then turn on them the next.
That can be argued back by saying - "if you do love me and intend to not leave me, then what's the hassle with signing a silly document anyways?"
The bigger question is - are you seriously considering marrying her? Or is it just a notion to think about further down the road AFTER you have met her in person? "A pretty nice girl so far" is a bit of a stretch of a reason to get married, in my opinion. Then again, I see couples that had dated for 10 years before getting married last but a few years.
I'm going to speculate that 1) she's super hot, and/or 2) that you guys must have made somewhat a connection for you to even consider marrying her without even meeting her in person. But that veers from your original question, so I will return to your original question, and vote YES, I think you should definitely get a prenup.