The tricky part is going to be figuring out how to freeze the milk and get it back before it completely thaws. If she just kept it refrigerated, it would only be good 8 days from when it was pumped, I'm not sure if she would be able to use it up that quickly. So, her best bet is probably to freeze it. It is only considered thawed once there is no ice crystals in the milk, so partially thawed is still fine. I'd check with
DCL to see if I could get a freezer for the trip. I used to store my milk in freezer bags made be Bailey. I loved these because they were very thick and durable. I remember trying to figure out the logistics once for a week business trip I had to do. I had a small freezer stash and could not afford to let any go to waste.
Here are the recommendations from the La Leche League:
Storage Guidelines
Storing milk in 2-4 ounce amounts may reduce waste. Refrigerated milk has more anti-infective properties than frozen milk. Cool milk in refrigerator before adding to frozen milk.
Human milk can be stored
at room temperature (66-72°F, 19-22°C) for up to 10 hours
in a refrigerator (32-39°F, 0-4°C) for up to 8 days
in a freezer compartment inside a refrigerator (variable temperature due to the door opening frequently) for up to 2 weeks
in a freezer compartment with a separate door (variable temperature due to the door opening frequently) for up to 3 to 4 months.
in a separate deep freeze (0°F, -19°C) for up to 6 months or longer.
What Type of Container to Use
Refrigerated or frozen milk may be stored in:
hard-sided plastic or glass containers with well-fitting tops
freezer milk bags that are designed for storing human milk
Disposable bottle liners are not recommended.