Watch when Lydia returns from the Faucet farm. She gets out of the car and Mitch runs to her followed by Melanie. Melanie (who is payed by 'Tippi' Hedron) has her hair down to her shoulders, where as her hair is up for the entire film but this shot. I don't think this is 'Tippi' because her face is not seen when she runs to Lydia.