When is it OK to date a friend's ex?
Mostly unbiased, always genuine advice from Dear G.
Now, let's say fate has nothing to do with this and that running into your friend's ex was totally random and not all that remarkable when you consider that statistical probability of it.
This doesn't mean that you and the ex don't have a connection; it just means that running into him isn't some sign from the universe that you're meant to be. So you have to let go of that idea and stop peddling it as justification.
As for telling your friend, yes, do it. Be honest. Just don't mention fate.
Which brings us to the second part of your question: Does she have a right to be upset about things? Your question presumes that she will be upset and you're probably correct. Sure, it's great that she's with someone new and that fact may lessen the blow. But it's still gonna smart to know that her friend has the hots for her ex and that he might reciprocate those feelings.
So the question is less about whether or not she has a right to be upset, but whether or not she will/should get over it, eventually. If you believe in Girl Code—never date a friend's ex—then what you're doing is in violation and, as such, unforgivable.
But in subsection (d)(3)(A)(iii) of Girl Code, there's a clause that states: "If sufficient time has passed (with 'sufficient time' defined as the number of years of the original relationship multiplied by three), AND if said friend is VERY seriously dating someone new (with 'VERY seriously dating' defined as cohabiting and/or engaged), AND if you have been honest and open with her from the beginning, then dating said friend's said ex is permissible."
Of course, this doesn't mean that your friend will be totally cool with things. That's a risk you have to be willing to take, along with the risk that you might have totally misjudged the spark between you and the ex, which would suck.
Yours in doing our best,
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