Clutch was slipping and engine was revving high

So my clutch had been slipping for a minute now, the engine was revving high in every gear when I tried to accelerate. I was not going as fast as indicated by the revolutions, but it would eventually settle down and accelerate at a somewhat normal pace if I baby-ed it. I knew that meant the clutch was going out, the clutch plate wearing down right? Which did not really surprise me, it was the original clutch from the manufacturer, making it like 40,000 miles overdue for a change. So I should have changed it at the first signs, but I did not, guess I hoped I could just wait until I was ready. Anyways, I was headed up the highway for a fourth anniversary dinner with my girl on new years day, and the speed limit changed to sixty five, so I go to accelerate from sixty to seventy and it just would not, my baby could not make it. Ripped my heart out. I was around 3000 rpms in fifth gear at sixty and when I depressed the accelerator the engine shot to 5000 to 5500 and I did not go a place. I maintained sixty mph but it sounded like I was running her out as far as she could go, I downshifted to fourth to see if it was the gear and the engine did the same thing with no acceleration, so I went back to fifth and tried to make it to the next exit. Sixty mph was getting hard for the Subi and I did not want to blow the engine, but I could not touch the gas without it rocketing up, not a redline but close. I was almost to an exit and there was a pretty loud boom and the clutch pedal hit the floor. I cannot remember if I pulled out of gear or if the car did. But I turned on the hazards and rolled half on, half off the road to the exit median and turned the car off. It definitely smelled like burned clutch, still smells that way today. I got towed home, but now I have to fix her. The way the pedal hit the floor and stayed I was thinking slave cylinder, but I cannot be sure. When I pulled the pedal back up with my hand it stayed and when I depress it, it comes back up. It would not shift into gear with the clutch down, but it will crank and run just seems a little rough. I am going to buy a new clutch and install it but I need to know if that will fix it or if I should replace the slave cylinder too. This is my first car and I love her. I left home on foot and traveled around and worked on farms all last summer to pay for her. I bought her in Wyoming and drove all the way back home 1,584 miles to North Carolina with no tag and we made it, so I think she wants to be with me. I definitely want to do her good so please help if you can. Thanks.