Use Pure or Vitalite instead of butter/marg. If she just needs to be lactose free, there are lots of options. There's a company called lactofree (I think) that do milk, cheese etc it's ordinary milk, just missing the lactose. If it's dairy free, try soya products, milk, cheese, yoghurts etc. If the GP suggested it, have they prescribed you a special formula if she's only 9m? You can use this as you would milk in cooking on cereal etc.
Best advice is to read the labels on everything! Organix crisps are generally ok. The value ranges in supermarkets are often dairy free (tesco value bourbons for example). Check your bread, alot have milk in them. Home cooking will be easiest as you can omit what you need to. Freeze any leftovers in LO-sized portions so she has something to eat on occasions you're desperate for a curry or pizza!
There are a few jars & tray meals that have no milk which are handy to have a couple of in the cupboard, again it's just a case of reading the labels. Go shopping without her if you can as it'll take you a while the first time.