Complex sentence: According to sources, Martins became bored with her "dull" life and resolved to transform the environment around her, beginning in 1945 with an obsessive project to decorate her home and garden.
Split into simpler sentences: According to sources, Martins became bored with her "dull" life and resolved to transform the environment around her. She began an obsessive project around 1945 to decorate her home and garden.