The feeling's mutual
If you both like each other and think that there could be something really worth exploring between the two of you then ultimately you should go for it.
However there are ways of going about it. Jo says: "Take it slowly and discreetly."
The idea of rushing into a relationship with your friend's ex with no consideration of her feelings is not a good one.
"The impact of dating your friend’s ex has wider reaching consequences than just your friend – it can affect the whole dynamic of your social circle.
So while it’s best to admit that you’re dating, don’t expect to be able to integrate instantly into the same circle of shared friends."