Please tell your coworker to STOP feeding cooked bones, it can cause deadly injuries
No cooked meat, raw is better for the cat as they need their taurine and taurine is destroyed by cooking. The dog food may not contain any as it is not an essential nutrient for dogs. Beef is quite high in taurine so kitty will get it from there.
Do not worry about the richness of beef, cats don't have a problem with meat protein as dogs do, they are carnivores. The only issue with ground beef is the possibility of ecoli being present due to the grinding of the meat.