Translation:Instead my mother recognized him right away.
"When lo and la are followed by ho, hai, ha, abbiamo, avete and hanno, they drop the vowel and are spelled l’."
UK, Collins (2011-10-31). Collins Easy Learning Italian Grammar (Italian Edition) (Kindle Locations 2252-2257). HarperCollins UK. Kindle Edition.
Duo seems to require it, at least most of the time
Edit Just found this: "Elision is optional with lo and la, but is especially common in l'ho and l'ha " Maiden & Robustelli, page 97