1. It is a clear case of bad marriage for your sister in law,
2. It is a mistake to succumb to the demand of the groom party to arrange the marriage ceremony in a 5 start hotel,
3. Decide what do you want from this relationship now since it is apparent that she has no place in her husband's home and mind now and also that her inlaws are geedy people,
4. She can lodge a police complaint u/s498A of IPC, file DV acse claiming maintenance and residenbtial right and protection,
5. She can also file a divorce case after one year of marriage claiming substantial amount towards compensation/alimony,
6. Let her start her life afresh rather thatn ruining it in the criminal custody of her in laws.