Bad start to the day :(

[sunnydays]

Well...I see this a bit differently. If this is the only issue with this client, I would not be terminating without first at least trying to solve the problem. Instead, I would tell the parent exactly what you are feeling in a professional way. Tell her calmly that you did not like the way she had spoken to you and explain exactly the reasons. If you stay calm and talk to her politely, you may find that she just didn't realize she was overstepping her boundaries. At least give her the chance to redeem herself in my opinon before jumping to termination over one incident.