I really think the plant debris by the front door matches the purple flowers seen along the walkway (likely ruellia / Mexican petunia). If that’s true, it raises the possibility that someone approached from that direction and unintentionally tracked plant material right up to the entry, either on shoes/clothing, or possibly by staying low/crawling to reduce visibility to the doorbell camera.
What also stands out is the green smudge/marking near the doorbell area, which looks consistent with plant transfer (like brushing against a stem or leaves). And since doorbells are typically mounted around 48–54 inches, contact in that area may be more naturally explained by someone taller than Nancy (5’5”). A person around 5’10” would be more likely to brush that height with their shoulder/upper arm. That said, Nancy could still have made contact if she stumbled, raised an arm, leaned into the frame, or was being pulled.
The presence of this debris near the entry feels like a detail that could matter.