How safe a woman feels with you, who you are, should make the biggest difference. If she has had experience with someone who is large and deliberately pushed his hard penis into her in a hard thrusting fashion she may be fearful of YOU doing that, because that can be very painful. Being gentle and loving and showing her that you won't hurt her with your strong arms, hands will go a long way to making her feel safe. Show her gentleness in your lovemaking touch, and when you enter her gently, slowly and not forcefully she'll know you want it to be good and not painful. Of course, asking her how it feels as you are moving into her gives her permission to let you know if it does start to be a problem. Open communication is the best way for her to feel safe. If you are having sex with someone without connections and communication beforehand, little can be done to help her feel safe.
