The fact that she called back and said let me think about it says that she did like him, but he set off a ton of red flags and she needs more time to reflect on what happened/ask friends what they think. In no particular order.
1. You didn't ask right away
2. You called
3. You hung up, when you didn't get your way.
4 through 9. You called again, didn't get your way again, and hung up again. (Huge flag)
Don't you dare contact this woman again unless she contacts you first. You look needy, passive, desperate and someone that gets mad to easily. If she gives you a chance you better take her on the best 1st date ever, you are already on your last chance.