In act IV, scene VII, of Shakespeare's Hamlet, what is notable about Gertrude’s words about Ophelia’s death?

Gertrude says that Ophelia has drowned. She was watching Ophelia play in the branches of a willow by the water when she fell in. Gertrude says that Ophelia seemed ignorant of danger and went to her death slowly, singing songs. Gertrude describes her as dying almost in slow motion: “Her clothes spread wide, / And mermaid-like awhile they bore her up, / Which time she chanted snatches of old lauds, / As one incapable of her own distress, / Or like a creature native and indued / Unto that element.” Indeed, the question to ask given this description is not, “Did Ophelia kill herself?” but rather, “If she had time to sing songs while dying, why on earth didn’t Gertrude try to save her?” Perhaps, though (as suggested in the television series, Slings & Arrows, among other places), Gertrude's narrative is an attempt to protect Ophelia. She knows that Ophelia is better off dead and tries to hide the fact of her suicide with her narrative. As with so many aspects of this play, the truth is not forthcoming.