need cheapest, USABLE mic/interface for vocal scratch tracks

I have a singer that just got a budget laptop (a Lenovo B575, windows 7 operating system), but at least has 4 USB inputs. She needs the least expensive interface/mic possible. Quality isn't an issue as she will record her vocal tracks at my studio in the end, but something where I can email her MP3 files and she can add a vocal demo (ideas) track and email back.  Also, she can practice her vocal tracks and at least hear them back. Will set her up with Audacity or Reaper and I have mics for her to use, and even some high impedance if necessary.  Down the line, maybe get more advanced, but JUST THE BASIC for now.

Need something for next to NOTHING.... she is a single mom on a tight budget

I've seen these XLR to USB cables, but the reviews say they are total junk. Are there $35 USB mics that actually work or an interface in that price range?
I want to keep the cheap as possible, but obviously don't want to just record static or give her problems.

Try looking for an AT2020USB or a Samson C01USB on eBay - they sell them used there all the time for 20-35$..and forget those who are trying to sell near retail (those are for suckers).
 
It'll do the job nicely, will use standard system drivers (no need for special drivers) and they're not terribly awful sounding either. 

I will mention this. If you got a soundcard in the computer to play music with and can set it up to also record with, then the mic that came with the soundcard (they use to have those) will not be very good, but it will work.
People make videos and photos with what they got with the computer.
?? Of course it may not function for making a recording but people use their built-in webcams and anything else that came with the computer. Just have to try it and become familiar with it and see if it can be done with a program used to record music or sound with.
With a computer mic a person may have to hold it a at least half a foot to a foot away though and it will pick up ambient sounds all around also. It probably is more omni-directional than anything else. Afterall those really cheap computer mics are still condensers and the microphone plug-in to the sound card provides I think some kind of voltage to it also. I think that is it, but never really looked at all the workings of it, just plugged it in to the sound card and adjust the input in Windows and used it the best that can be done. They do have computer games that have chats like in multiplayer games that people talk a little over the connection by pressing the talk key and even with some forums in a chat forum where people use a microphone with the computer to give a talk with over the Internet or with their computer for real-time events.