Old B&W movie with electrified car in final scene?

Can anyone help with identifying this old B & W movie – probably American, from the 40s or 50s? In the final scene there has been a car crash and the car has become electrified. A man is trying to help a teenage girl out and tells her not to step on any metal parts of the car as she gets out, or she will be electrocuted. As she is getting out she sees a sparkly brooch or pin on the car floor – t might be a butterfly design. She wants to pick it up. I can’t remember what happens after that.
In the middle of the movie I think there is a woman thief who is on the run and she dyes her long hair in a motel room to disguise herself. She either dyes it from blonde to black or from black to blonde, I can’t remember which.
I saw this movie on tv when I was a child in the late 60s.

Got something to say?