I knew a mother who, on returning to work (her baby was 4 months old), found that her baby was not interested in milk of any kind at day care. She was fine eating solids and drinking water, but she wanted her mama for her milk. Surprisingly, this worked out well for them. The baby nursed frequently in the evening and at night. The mother seemed to sleep enough.
Your partner is going back to work much earlier, so I think the main concern is the possibility of nipple confusion from being given a bottle. This is a real danger; although of course it doesn't happen to every baby that is given a bottle at day care.
About the expressing at work. Whether she chooses hand expression or electric pumping, it's a matter of practicing, so that the let down works as well as it does with baby. It will be helpful for her to start practicing this at home where she feels as relaxed as possible.
In principle, a woman can pump at her desk.
Practicing pumping in public is the key. As long as she is matter-of-fact and cool about it, others will be too.
A couple of ways around giving a bottle:
1. Use a paper or slightly flexible plastic cup, and bending it to make a spout. You can dribble the milk into baby's mouth slowing using the spout.
2. Use the Medela SNS or Lactaid supplementer. These supplementers are often used for feeding preemies and adopted babies, with the narrow, flexible tube and the nipple going into baby's mouth. The milk only flows through the tube when active sucking occurs, because of the tiny diameter of the tube. You can also feed the baby with the tube and your little finger instead of a nipple. Same principle -- baby still has to work, sucking, with the same strength as at the breast, and will therefore not go on strike at the breast.
If the two of you are interested in this option, you can do a lot to make it work, by learning how to do one feeding per 24 hours with this approach. Once you are comfortable doing it, it will be easier for you to teach the day care provider how to do it.
As you approach the back-to-work target date, you could add another daytime feeding, with your partner doing more daytime pumping or expressing. With all transitions in breastfeeding, the more step by step you can go, the better.
You might consider visiting the daycare once during the day to do one of these feedings.