@ Rinku,
According to standard astrology and based on sun sign or moon sign, if she has worn the emerald a lot of harm has already been inflicted.
Secondly, it is not mentioned why she started wearing it and why you would want to remove it.
The same thing goes for Ruby; why do she wish to wear it.
Emerald is a stone for Budha/Mercury, so for marriage matters it is not advisable to wear (this advise is not based on your sister’s personal horoscope).
Ruby is for Sun and is considered to increase self-esteem as well as ego, depending on personalized factors of the individual’s horoscope if it increases the ego, then marriage may not work.
Wishing you good luck, may God bless you and above all!!!
CHEERS!!!