My Mother-in-law to be is in a verbally abusive relationship

My Mother-in-law to be is in a verbally abusive. Her abuser is her live in boyfriend. She is to be talking care of her elderly father who has dementia and her 17 year old son. She doesn't realize he is abusing him. She feels he loves her so much. They are taking her father's money and using it for their own fun. They just stick him in the VA hospice program for 5 days so they can use his money to remodel his house to where when he gets home he will be even more confused as to what's going on as he is already. My fiance and I feel so helpless in this situation. Any advice and prayers are greatly appreciated. Thank you in advance