Why would she object to pork and veal? They add a subtler texture and taste which is what you want in a bolognese. It's not a pasta meat sauce per se. If that's what you want then you should be using a lean ground chuck, and browned mushrooms - which adds to the beef flavour. Even for a regular meat sauce I'll always use all 3 where possible. Luckily for me one of my local supermarkets regularly sells packages of all three for that express purpose! And never forget a good Italian tomato paste in either!!! If you're not using tomato paste don't bother making it!!!!!!!!!!!!