Absolutely not. Had she known, she would have been a willing party to the murder. She would have had to have been someone like Lady Macbeth. And it is quite clear in Act III Scene 4 when Hamlet says "Almost as bad, dear mother, as kill a king and marry with his brother," she is shocked and horrified. Had she been guilty, she would have denied it. But instead she says "As kill a king?" as if he had never thought about that before. It's like saying "You mean he was murdered?" Her behaviour is quite inconsistent with her having suspected that King Hamlet was murdered.
Aids.
Gertrude, Hamlets mother.
Hamlet is talking to the Ghost, which Gertrude can't see, which looks bizarre to her. For the first time, Gertrude sees Hamlet as seriously mentally ill, not just disturbed. Ironically, it's Gertrude whose perceptions are faulty in this scene.
Hamlet kills Claudius by stabbing him with the poisoned sword Laertes carried and by forcing Claudius to drink the dregs of the poisoned drink which killed Gertrude.
Polonius is listening to Lord Hamlet's meeting with Gertrude behind the curtain.
Gertrude of Sulzbach died in 1146.
Gertrude of Süpplingenburg died in 1143.
Gertrude of Dagsburg died in 1225.
Gertrude of Aldenberg died in 1297.
Gertrude Morgan died in 1980.
Gertrude Johnson died in 1973.
Gertrude Appleyard died in 1917.
Gertrude Bloede died in 1905.
Gertrude Melville died in 1959.
Gertrude of Austria died in 1288.
Gertrude of Baden died in 1225.
Gertrude Meredith died in 1986.