94 Blazer oooops

We loaned our 94 blazer to our room mate to go to jury duty. It was a very cold foggy morning. She got about 15 miles down the freeway and it started lurching and smoking. We called the tow truck and had it brought home. We found that instead of turning off the rear window defroster she had hit the low 4 wheel drive button. She said she was going 65 mph when she decided she needed to pull it over. I am amazed that it could go 65 in low 4 and drive. She said it wouldn't go any faster than that. It looks like the fluid came out the vent up in the engjine compartment. The back end is coated from it blowing back. Do you think it is ruined, or should we try adding fluid and see what happens. It still moves in 2 wheel drive with no noises. We are really hoping it is not ruined. She feels really bad. Your input will be much appreciated.