How to Find History of Shares

My mom has a stock certificate issued to her on May 5, 2000 for 88 shares of GE stock. Her current investment manager says that she has 16 shares of GE Aerospace, 5 shares of GE Healthcare, and 4 shares of GE Vernova. I've read about splits, reverse splits, and the corp split of GE into GE, GEV, and GEHC but for the life of me I cannot figure how those 88 GE shares turned into only 16 GE Aerospace. I calculated out all the splits and reverse splits and the allocation of the Corporate level splits, but it just doesn't math out. Does anyone have a handy tool for figuring this? As i see it, there must have been a sale somewhere in the past 26 years. I know for a fact she hasn't sold in the past 15 years, but before that I can't be sure because my dad managed everything. How do I find the transaction history of these shares? She didn't have them in a brokerage account until last week. Do we contact GE?