It is perfectly legitimate to worry or be afraid about some guy you meet in person from a dating site taking advantage of you due to your short and petite stature. The good news is that the experience of by far the majority of girls who use dating sites, whether they be short and petite or not, is not what you fear.
Yes, they could meet a creep or an obnoxious guy, but their safety isn’t typically in question. Exercise the same safety protocols you would with any stranger that you are meeting with on an official first date.
Meet at a public place. Don’t disclose where you live or work. Keep your personal items with you at all times. Always be vigilant about what you drink and consume and how you go about doing it. Let someone you know and trust be aware of who this guy is and where you are meeting him.
For the most part, the guys you meet on dating sites are the same guys you see at your workplace, grocery store, gas station, gym, public park, mall, etc. They are just using an online medium to find someone. Practice common sense safety measures and you will have nothing to fear.