Also she has 2 disks cause it was C and D, but when she opens the case we could only find one, not sure why
Based on the product ID in the first screenshot, this is an HP workstation PC with a 4th gen intel processor. It is very unlikely that there is more than one drive in the computer, especially if you can only locate one. It is also very unlikely that this computer has an SSD unless you put one in yourself. If you were seeing a C and D, it was almost certainly because the one physical drive was partitioned into two different logical drives. Knowing HP, the D drive was likely a recovery partition unless you were actually storing data in it.
You can replace the drive with either a SATA SSD or a normal SATA HDD, though unless you're storing a huge amount of data, I would just recommend the SSD at this point for performence. Just be aware you will have to reinstall Windows on the new drive, so make sure you have or are able to create an install drive for Windows.