Looking at the horoscope of your sister, her Rahu is with Jupiter forming the guru chandal dosha, which is never good, as Jupiter is the karka for husband. Yes there is a possibility of a second marriage, not necessary to person she may know and the period is going on. Marital bliss can be achieved only through proper matching of the horoscopes.
Blessings,
Navneet Khanna
Astrologer