"She told us that she was your mother."
अनुवाद:उन्होंने हमें बताया कि वे तुम्हारी माँ थीं।
Again the mistake between She and They. As उन्होंने is an plural mode of narrative, so They will be appropriate answer.
Both sentence of English and hindi is perfect here. I am so confused about these unnecessary comments here as I am still thinking that we are in English learning section so why anyone is focusing on hindi. The translation in hindi is in that form where anyone can understand easily and in other word this app is for get the fluency in basic phrases. It's not for hindi learner instead it's for English learners.