Me and my sister are twins and both nearsighted, she says when she wakes up she sees 20/20 vision, thats never happened to me, how is that possible?

Many factors: You and your sister probably do now have the same glasses prescription, because many environmental factors can affect the prescription over the years. Identical twins do not necessarily have the same glasses prescription anyway, although they may be similar. So, why is your sister 20/20 upon awakening (distance vision)? This might actually indicate a problem with her eyes rather than yours!