Amateur stepsister invites me to try her new lingerie, while her boyfriend cheats on her with a friend and she desires me to take her

My beautiful stepsis caught me staring at her new lingerie and playfully asked me to try it on. Unbeknownst to her, her boyfriend was cheating on her with our mutual friend. The situation ignited a desire in her to confront him, and she eagerly invited me to join her in a wild encounter.