Complex sentence: They pointed out that despite her slow progress with language she had clearly progressed in other aspects of her psychological development, and throughout most of the time they were testing her she seemed to be happy with life in general.
Split into simpler sentences: They pointed out that despite her slow progress with language, she had clearly progressed in other aspects of her psychological development. Furthermore, they wrote that throughout most of the time they were testing her she seemed to be happy with life in general.