The answer to your question is as it follows:
If girl agreed and got married with the person only for the sake of her mother’s happiness, the Nikah will take place. In this case, preferring mother’s happiness over her own is also worthy of reward.
And Allah knows best
Darul Uloom Waqf Deoband
This answer was collected from the official website of Darul Uloom Deoband Waqf. The institution is based in India and the answers are provided in accordance to the Hanafi Fiqh.