Is it permissible to marry the elder daughter of a maternal uncle if she does not consent due to the age difference?

There is no religious impediment for a man to marry a woman older than him, or vice versa, if they both agree. The Prophet, peace and blessings be upon him, married Khadijah, may Allah be pleased with her, and she was older than him. He also married Aishah, may Allah be pleased with her, and she was younger than him. Umar ibn al-Khattab, may Allah be pleased with him, married the daughter of Ali ibn Abi Talib, may Allah be pleased with him, and she was much younger than him, and there was no harm in that. Therefore, the age difference is not a barrier to your marriage to your maternal cousin's daughter if she accepts you as a husband.