I still wouldn't do it. Why is it so urgent that it can't wait until everything settles down, and you either a) get some eggs - and keep them yourself - or b) wait until you know for sure she isn't gravid?

If the buyer is still interested, they should be willing to wait. Circumstances change, and you want to be honest and uphold your end of the bargain, of course, however as you've mentioned the other party seems professional and trustworthy. So why not wait?