The first incident took place on October 11. Rimene's partner told her that their neighbour had a crush on her; Rimene went to the neighbour's house to confront her about it.
The neighbour was 16 weeks pregnant at the time.
The girl denied having a crush. Rimene left and returned later; forcing entry through a locked door.
She found the girl lying in bed, punched her in the face and pushed her into a wardrobe.
The second incident took place on October 21 after Rimene's partner told her she wanted to live at another address. Rimene became angry and told her to leave.
The complainant left and went to stay with her mother; Rimene showed up at the mother's house, threw two bags of the complainant's possessions at her, and punched her in the face twice.
She followed her to the kitchen and knocked her to the floor, punched her again, grabbed her by her hair and smashed her head into the floor numerous times.
The complainant was admitted to hospital with a mild concussion, multiple contusions and scratches.
The third incident occurred on February 14, when Rimene breached a protection order by confronting the complainant and hitting her in the back of the head with an unknown object.
Defence lawyer Peter Stevens said he did not think he could argue against a term of imprisonment but asked that the judge impose a short sentence.
Judge Bill Hastings said Rimene had expressed no remorse for what she had done and blamed the victims. He said the 15-year-old victim had moved in with her mother because she was afraid to live by herself.
"She writes that she has miscarried due to the stress she believes you have caused her," he said.
Judge Hastings said the offences are all linked by violence.
"The aggravating factors are that they involved actual violence ... unlawful entry into a dwelling place, they involved physical harm. One of the victims was particularly vulnerable because of her age and her pregnancy.
"There is evidence of obsession and stalk which is mitigated, to some extent, by your addiction issues," he said.
He sentenced Rimene to nine months' imprisonment. He also imposed that she undertake any programmes or counselling deemed as necessary to address issues of domestic violence and alcohol or drug addiction.
He said the purpose of the sentence was, among other things, to protect the community.
