We should see movements on our petitions by late June/ early to mid July. You may receive the NOA2 while you're away in Europe. You can always delay the interview by a few months and write into the embassy to see if you can extend the expiration of your petition to delay it a little longer. That way you can have some extra cushion between the NOA2 and her migrating to the US. Once she receives her visa she has 6 months to enter to the US, depending on if her medical is still valid. I would recommend she enter before her medical expires. So she can definitely migrate to the US after the first of the year and still have everything valid.