Greasy Hair or Residue?

Please help me find a solution!
My daughter is 18, and cannot seem to get her hair clean.  She uses a variety of clarifying shampoos daily, only conditions the ends, and rinses thoroughly.  But minerals in well water, or chemicals in city water, seem to cling to her hair and leave a residue.  She has several cowlicks, so the greasy strands bump out making a mess.  She is tired of only wearing pony tails!  When she gets a professional clarifying treatment, the results are lovely for a couple days.  But once she has shampooed two or three times, the residue returns.  Her father also has a similar issue, but it is not as noticable on his short hair.  The rest of the family suffers no ill effects.  He is of Mediterranean decent, and I'm wondering if this seemingly "porous" hair is genetic.  Has anybody experienced something similar?  Does anybody have any suggestions?  Thanks in advance for any help you can offer.

How often does your daughter wash her hair?  Actually, washing the hair more often will stimulate the sebaceous glands to produce more sebum (oil).  Have you considered installing a shower filter? They can really help with chemical and/or mineral buildup depending on the type of filter that is used.  My hair is fine with an oily scalp and could definatley wash my hair everyday, but wash it every other day instead.

OP