A.D.
You are at the whim of the TSA agents, and to anyone, 25 bags is going to be considered excessive. I would bring whatever amount you will need for the flight and wait times in the airport and then double it in case of flight delays, etc. (you may even want to make a little chart to stick in the bag that includes feeding times, flights and your rationale - because if you double it, they could consider that excessive).
When I traveled without my daughter for work, I pumped while I was away and Fedexed milk back to my husband in a little cooler with double ziplocked ice-packs. This worked very well. I'm not sure what the airlines restrictions are for checked coolers and ice. The problem is less one of lost luggage or the wrong destination (although this can happen too), but of the airline rejecting or disposing of the package due to its "unknown liquid" contents (which would include both the breastmilk and the ice). I know when they first put the new restrictions in place, the seafood and fishing industries were really hurt, people couldn't bring lobster home from Maine, or tuna and other big game fish home from Charter fishing trips. I think they solved some of the issues by packing things with bags of frozen corn or peas instead of ice, but since the breastmilk is itself a liquid, you would definitely need to check with the airlines before checking it as luggage.
Maybe you could make some more attempts at getting her to nurse for some of the feedings before your trip. Otherwise, I would ship the milk. Good luck!