There could be many reasons for hate
1) In some village even today girl child is thought as an extra responsibility because they have to get her married and take all nakras from the in law side after marriage. Amamji basically has never bent to anyone and may feel that if a girl child is born she has to behave nicely with girls in laws etc. Ammaji never bends to anyone if you observe in show.
2) Ammaji may have been treated a bit badly(does not look so since she keeps saying i used to play with guns from childhood) in her house or in laws initially(this also is remote possibility since her husband and in laws died when she was young)
3) Ammaji thinks that sons help her in her cruel activitites and girls cannot do all that (disproved by amba)
4) Its observed that in family and outside usually women do not like other women grabbing attention of the society, family etc. Only they want to be center of attraction.
Ex: Father in laws and Son in laws do not get jealous over daughter(Rare cases are exception)
But frequently we see mother in law and wife trying to get sons on anyone side. Why cannot they remain close to mother and wife after marriage? Ammaji has done this to jogi, avtaar, Raghav not allowing them to treat wife with love and respect as they do their mothers.
I think Reason 1 and Reason 4 is reason for ammaji hating girls. She did not hate amba when she realized she is daughter but does not like jhumar because amba is her own daughter. Even in real life rarely a mother hates a daughter although she has to make many compromises because of daughter sake, same as ammaji. But here also ammaji saved her life but drove her out of house because in remote villages where she lives daughter is seen as liability.