My mother relaxed my hair for years (in addition to the hairdresser).  She always did a great job, better than the hairdresser.  She would use Revlon Realistic Regular.  Now I just get it done at the salon and they use Cream of Nature. 

If you are both confident in her ability to get the job done then go for it.  I would be extra careful not to scratch, base your scalp and areas around the hairline (extra care to places where maybe you do end up scratching).  And as Renee said, be sure that your mother will not apply the relaxer to your ends and that she has a good gentle technique for smoothing the areas where the relaxer is applied.  Rinse your hair super well, be sure to have a neutralizer on hand, the ones that come with relaxer kits are good.  Wash the hair as many times as necessary (4-5 times).  (My personal picks: Bone Straight Neutralizing Shampoo and Porosity Control Conditioner which neutralizes and is very soothing after a relaxer).   

Do not use a children's relaxer thinking it is safer or gentler.  That is a misconception.  Choose a relaxer that is good for your hair type and that you trust will work well on your hair.  Ask your hairdresser which one they use (say your friend wants to know).  If they won't tell you, I can honestly say that I have used several brands that have all worked well (Revlon Realistic, Cream of Nature, Affirm).  There are many other very good brands out there and maybe more people on the boards can give your their recommendations.

Good luck.

P.S.  I would trust a hairdresser or my mother over myself any day to do a relaxer.  Even though I know the steps, I just don't have the confidence.  Go figure.