This Pioneer is as cheap as I'd go. Keep in mind the harness for that vehicle is pricey. I'd use the RP4-CH11 (don't use Metra/Axxess). If you buy the head unit from SonicElectronix or Crutchfield, they'll discount the harness for you. Also realize the model I linked does not have a CD player. For a young girl, they probably couldn't care less. It's all about Bluetooth and iPhone inputs, which it has. If you want the next step up, which I'd recommend, here's what I'd recommend. You pay $299 now (which is normal price for the 1400NEX anyway) and then has the choice to install and activate Sirius. If you do, you'll get $70 MIR. If you don't, $299 is still a decent price. But the 1400NEX will give you Apple CarPlay, which is wonderful if she's got an iPhone.
As for the backup cam, it really depends on how you want it mounted and such. Some will require holes to be drilled into the body of the car and others just screw around the license plate. It's all about the final look you want. Check out your local shop and ask what their thoughts are. Ask how much labor will be too.
Sooo few things. First, Amazon is not an authorized Pioneer dealer. So if you have an issue past Amazon's return policy, you will have no warranty. Second, the one I linked you to has a CD/DVD player. The one you linked to does not, but has the option for a couple bucks more. Third, and most importantly, you forgot the harness I linked you to. The RP4-CH11. This adapts aftermarket head units to your Liberty. That particular harness also retains steering wheel controls, so the ASWC is not needed if you're using the RP4. Forth, you forgot the other two parts you'll need which is a dash kit and antenna adapter. I didn't mention them because I assumed you'd order through Crutchfield or Sonic and they include them at no cost. Amazon does not. Fifth, the microbypass is mainly for watching video while driving. However, there are some select features that only become available when the vehicle is parked. Usually pairing new bluetooth devices and the like. Really nothing you'd need routinely. Up to you, but I wouldn't recommend it for a 16yr old.
You can buy the camera from anywhere you want. But I'd strongly recommend buying the head unit and parts from Crutchfield or SonicElectronix. The deal I linked you to is a solid price (only like $15 more than Amazon), you'll get full factory warranty, AND it includes some parts you'll need for the install at no charge. Again, ask for the RP4-CH11. Don't let them sell you on the Axxess CH harness and ASWC combo bullshit. Inferior products that are only like $10 cheaper. I install for a living. Trust me. They will discount the RP4-CH11 harness when you buy the head unit. If it's still more than Amazon has it for then let them give you the dash kit and antenna adapter for free and buy the RP4 harness from Amazon too.
Altogether, you're looking at maybe ~$370+ backup cam and sales tax from SonicElectronix. FWIW, I've been buying from Sonic for probably sheesh...over 10 years easy. Solid site. Call them and order over the phone if you'd like. Up to you. :-)