I have done this before… both when I chose to and when my pump failed. It would be best to talk to her doctor about it.
If it’s just for a couple days, then here is what I would recommend:
Disconnect the pump in the morning and about an hour later I would give the long lasting insulin (Lantus or Levemir). (The reason that I recommend waiting 1 hour is that she still will have active basal insulin in her from the pump.) The amount of Lantus or Levemir should be approximately the same as the amount of basal insulin that she gets through her pump in a day. I would check her blood sugar frequently in the first 6 hours of the transition to make sure that all is OK.
I think if she is only disconnecting for a few days, then it is simpler to give the basal injection just once per day. Take the Lantus/Levemir at the same time in the morning each day that she is disconnected from the pump. She should reconnect to the pump at the same time that she would take her Lantus or Levemir injection.
Again, I’m not a medical professional— so it would be best to ask her doctor, but this is the system that I would use. I did this for a week during our vacation in the summer and i quite enjoyed it