“Is there any way to prevent a tear in or outside the vagina during sex?”
Women may experience tearing if the vagina is too dry. This can be from a decrease in normal vaginal secretions or from condom use. Try a water soluble lubricant, like Astroglide or KY. Do not use Vaseline or any petroleum based lubricant. Additionally, sexual foreplay may help increase normal vaginal secretions.
Lastly, if you are engaging in rough sex, talk to your partner about boundaries.