Mrs.Smith complained to me that she often found it simply impossible to communicate with her daughter.
根据【史密斯太太对我抱怨说】明显是【已发生行为】故用过去时,从句与主句的动作没先后关系,即从句是一个现象,而不是某次特例,故也用一般过去时与主句时态一致.