Was Edna’s death really a suicide? Did she intend to kill herself when she set out to Grand Isle? To the Beach? Into the water?

Yes, Edna's death is a suicide.... it's a statement of freedom, a choice she makes because she refuses to give into expectations. I don't believe Edna went to the Isle intending to take her own life..... I believe it was a reaction. Edna's suicide is her way of asserting herself. She can take her lovers, flout convention, and destroy herself. Unfortunately, she decides to destroy herself completely in taking her own life, rather than sacrifice her life just to make other people happy.... to fulfill their expectations.