I rented a hospital grade double electric pump. All I had to purchase was the tubing, the collection bottles, and the parts that attached to my breasts. The milk NEVER entered the pump itself, just the washable components. I have heard that some pumps pump the milk through the machine and it is these kinds of pumps you would want to avoid because you cannot take the pump apart to clean it. Honestly, I've never seen any pumps that actually take the milk and push it through the machine but I suppose older pumps do. I don't know for sure.
BTW: on rented pumps, at least the one I had, the tubing was never to get wet so if your friend's pump has tubing, chances are it cannot get wet (it's primary function is for suction) so with that said, if it can't get wet, then NO milk is entering the pump. I hope this helps!
If you rent a pump from a hospital, they will make you purchase the plastic components which are the pieces that attach to your breast and the collection bottles. The pump I rented, the milk never went through the tubing that attached to the pump from the collection bottles. The tubing was really just for the suction. I would say you can safely sterilize the pieces from your friend's pump as long as you know that her milk never went INTO the pump itself. You wouldn't want your milk to be contaminated with bacteria and other unmentionables. But in all honesty, I don't think pumps today pull the milk through the pump. Ask your friend how her pump works or research it online.