After three weeks is a very short period of time to begin a new relationship especially when the last one lasted two and half years.

How she feels about the end of the last relationship may just be starting to hit her/take effect on her now and she may need time to decipher how she feels about this relationship and if she's really ready to begin again or not.

Respect her situation, give her time, and then she should come to you and let you know.