Does you DD take water from a cup? If so then when you aren't there she will probaby be happy to just have that where she would normally have little drink type breastfeeds. I am sure that those are about being thirsty, not hungry and water does the job. I have found with both my boys that once they were on solids they only really needed to have 3 or 4 decent feeds a day. They sometimes wanted extra little feeds in between but if they were/are being minded then it isn't an issue as the boobs aren't around to attract their attention.

My DS2 (9 months) is going into daycare for the first time tomorrow and I am just sending 1 EBM bottle along with him, aswell as his cup of water. I am pretty confident that with a feed just before being dropped off (around 7.30am), one just after being picked up (around 4pm), and one before bed he will be just fine. He can still have his other short feeds on the other days if he wants.

If you are concerned then try having a couple of feeds there for the first week or so, then cut it back if they aren't being used. It won't take long for you to work out how much your DD really wants when you aren't there.

As for expressing, I would think once a day will be fine unless you are finding it too uncomfortable to go that long. I am sure you can manage just fine without needing formula. And it will only get easier as DD gets older and the number of feeds she needs goes down.