My daughter will be flying from Atlanta to JFK via Delta. Then from JFK to Moscow via Aeroflot. Will she have to go through security checkpoints again when she switches over from domestic to international at JFK? Will the bags be automatically transferred?
The good news first - Delta do "interline" bags with Aeroflot, so she will be able to check the bags all the way through to Moscow. If the two flights are booked on the one ticket this should happen automatically. If they are on different tickets, then you will need to show a printout of the e-ticket when checking in with Delta. Either way, be sure to check that the luggage tags have "SVO" listed on them, which is the code for Moscow.
Now the bad news - Aeroflot operates out of Terminal 1 at JFK. Delta operates out of terminal s 2 and 3 (and from May, terminal 4). There is no air-side connection between terminals 1 and 2/3/4, so she will need to exit security and either walk to terminal 1, or catch the free "Airtran" between terminals and then re-clear security in terminal 1.
If she's also doing the return trip the story will be the same, except that she WILL need to collect her bags at JFK and re-check them. This is required due to US customs, and occurs regardless of whether Aeroflot tag the bags all the way through to Atlanta or not.
There is good news and not so good news.
The good news is that because Delta and Aeroflot codeshare your daughters bags will be checked in directly to the destination.
The not so good news is that Aeroflot is located in Terminal 1 and Delta flight will likely to arrive to Terminal 3. Delta does have a shuttle running between the terminals it operates in but it doesn't appear that it runs that shuttle to Terminal 1. So it is quite likely to necessitate going through security.