Back in August 2012 my oldest account on my report was 18 yrs and 11 mos. A long credit history was listed as one of the things helping my score.
In September 2012 my oldest account aged to 19 yrs and 0 mos. A short account history was listed as one of the things hurting my score.
I had been rebucketed from a bucket that included oldest account of 18 years to another bucket that included oldest account of some higher # of years (30 years, perhaps). Compared to people in the previous bucket I was stellar. Compared to people in the new bucket, my accounts were babies, as it were, and my accounts had to age to prove themselves.
I was happy to see this for a few reasons:
1. My score didn't budge during that time (no new accounts opened either, for anyone wondering)
2. It was listed higher on the list of things hurting my score in September than some other items that I wasn't truly sure how they were impacting my score. Specifically, it was listed as having more of an impact on my score than a missed payment I had from 9 months prior--fantastic! This indicated to me that the missed payment--while not good--wasn't quite as bad as I had thought it was, thereby affording me a little relief.
3. Since the age of my oldest account is now listed as a negative, that means I have the opportunity to allow my score to increase even higher than it could have in the previous bucket, simply by allowing time to pass. Time-consuming, to be sure, but very easy to do, and I look forward to the opportunity to increase my score in this manner! 
In summation, I wouldn't worry too much about a negative that says your account history is too short when the oldest account is 23 years old.
Good luck to you and your mom!
