i totally disagree with all those that are saying that they should move out, if her in laws are already resentful towards her they will hate her, and she will be the evil bahu who took their son away from them
i know your friend is in a very difficult situation but your friend needs to make an effort with the family...ignore the saas's sarcasm and what went on between the parents...she needs to concentrate on her own future.
she should try and get involved in the household chores as much as possible, even though they have a maid...uss ko chaye ke woh ghar ke eik eik kone me bass jaye and she needs to almost take over the household, and treat it as she treated her parents house...fair enough she's working but that's life, she has chosen to work and now needs to make time for her new family as well....
furthermore you asked "Is this normal in just 6 months of marriage?"...no this isn't normal, they should be enjoying each others company and not be worrying about money and what happened in the past...
Compromise and sabr are the two importnat things, once she is accepted in the family and has made her 'mukam' in the household things will get easier....she needs to be headstrong and keep her mouth zipped, it will take time but she needs to endure it all patiently and concentrate on strengthening the bond between husband and wife.