maybe a little regurg or she is having pains while feeding?
This is usually what happens with DS (although it is one feed it is EVERY feed is like this).

I find if i feed him in the sling or upright he is better and doesnt pull off crying like he does laying back or down flat. Perhaps try that?

Well Ethan woke 5 times last night. i ended up feeding him and keeping him in bed with me. During the day he is happy to sleep in his bassinetter for 3 hr at a time.. so no idea what th difference is. Maybe i will leave his light on all night ... lol