She'll probably be inclined to bf more often when you're around to make up for the missed feeds. She's old enough to be offered what ebm you have and water while you're away from her. If you bf her before you leave and as soon as you return and she has water and ebm on hand JIC while you're gone she'll be completely fine. You might find that even with only a small amount being expressed, you want to express while you're at work for comfort at least once during the day.

GL with returning to work!