Complex sentence: Cassie and Matthew begin to go down a similar path, but when they go to meet, he first stands her up and then, on a following meeting, proceeds to rip up a letter that she had sent and make fun of her.
Split into simpler sentences: Cassie and Matthew begin to go down a similar path and plan a meeting. However, he first stands her up and then, on a following meeting, proceeds to rip up a letter that she had sent and make fun of her.