My first question is- does your turn out come all the way from your hips, or are you more turned out at the feet ths n at the knees and upper level? In order for your ankles to be properly aligned and to be able to strengthen them, your turn out needs to be the same rotation form your hips all the way down to your feet. Your ankles really should be strong already BEFORE putting on pointe shoes, or the risk of injury is imminent.
A good exercise to help both your feet and ankles are press releves in parallel in regular ballet slippers. You need to be sure to keep your weight evenly distributed in the ball of the foot (no rolling toward the big or little toe), and fully extending and activating your ankle at the top of your releve. Roll up and down slowly, really paying attention to keeping your foot fully aligned. I recommend working in sets of 12 with breaks in between, and slowly building up the number of sets you do. Be sure to do calf strectches in between to keep your Achilles supple and your calf muscles long.