You can let your mom keep her cream and her victory — just understand what's actually winning. Collagen molecules are far too large to pass through the skin barrier; rubbed on top, they can't reach the dermis where your own collagen lives, so a "collagen cream" cannot restock collagen the way the name implies. What it can do — and visibly does — is act as a rich moisturizer: collagen is a protein that holds water and forms a smoothing film, so skin looks plumper and fine lines soften while it's on. If she's used it faithfully for years, she's been getting excellent, consistent moisturization, and consistency is genuinely a huge share of good skin. Her results are real; the mechanism on the jar isn't.
If she (or you) wanted ingredients that actually push skin to make more of its own collagen, the evidence ranking is clear: retinoids first — biopsy-verified collagen rebuilding in sun-damaged skin, decades of trials (https://pubmed.ncbi.nlm.nih.gov/3336176/) — with daily sunscreen as the thing that stops collagen being degraded in the first place (https://pubmed.ncbi.nlm.nih.gov/23732711/). Peptides, the more modern "collagen signal" ingredients, have modest but real early evidence (https://pubmed.ncbi.nlm.nih.gov/18492182/) — a fair middle option, oversold at the margins.
As for oral collagen supplements: some small industry-funded trials show modest hydration/elasticity changes; the independent evidence is thin. Not crazy, not proven.
Steal the cream if you like the texture. Add SPF and a retinoid if you want the mechanism.