1) your niece should file DV case and seek right to stay in matrimonial home , maintenance , protection order against her husband and in laws
2) DV is a continuing offence and can be filed even now
3) your neice can also filed 498A case against husband and in laws
4) no need to file application under section 125
CRPC
5) she can also file RCR if she so desires . Even if she obtains decree of RCR she cannot force her husband to stay with her