Foreigners often make some strange mistakes in Chinese when they study the most difficult language--- ---Chinese. We try to analyze typical sentences to correct these errors.

          Tā xiǎnɡxiǎnɡ xuéhuì dǎqiú.
False: 她想想学会打球。
          Tā xiǎnɡ xuéhuì dǎqiú.
True: 她想学会打球。

句中“想”做能源动词用。能源动词的语法特点之一是不能叠用，应当把“想想”改成“想”。
想 in the present sentence functions as an auxiliary verb which can not be reduplicated by characterisitic. One ought to substitute 想想 with a single 想.