My Sister Of Eternal Flower: The female lead has an intellectual disability. She never gives up and is a good person. The male lead doesn't like her at first but gradually warms up to her because she is a good person.
Pure: The female lead is a savant artist. A really sweet old school romance. The ending is sad. I enjoyed the show so much and found the ending so sad that I wish I didn't watch the last episode!
There are a lot of Chinese historical dramas (usually the ones with very young female lead characters) and modern high school dramas where the female lead is not very bright. Especially the high school dramas, I'd say at least 75% of the ones I have watched the female lead is at the bottom of her class and struggles with school. I don't have any specific suggestions for these categories but I thought I would mention it so you know what genres to look into that have a lot of this type of female lead.
