What is the exact model number of her computer as the 3000 series takes in a number of laptops? And did her system come with Windows 7 as the 3000 series in general were Windows 10 I believe. Possibly depending on the chipset in her system you can get the chipset drivers (which is probably what you need) from AMD or Intel. Now one further observation. I would also suggest updating your friend's system to Windows 10. It can still be done for free using the Windows 7 key. I suggest that due to the fact that, as you know, Windows 7 is no longer supported so that leaves the laptop wide open for virus and security issues.
Trying to help out a senior friend. Her laptop computer (Inspiron 15 3000 series) is running Windows 7 Pro. I have found all the device drivers, but four. Ethernet controller, Network controller, PCI simple communication controller and USB2.0-CRW. Sure would appreciate any help with finding these drivers for her? Thanks in advance, Bill Osborne     
Device drivers