Single mum with a 21 month old daughter. is she hitting milestones?

My daughter and I have been alone together since she was 6 months old. She has been checked out by doctors and is hitting her milestones physicaly. I'm starting to worry now that her development with speaking and listening and following simple comands aren't what they should be. I work part time whilst she goes to nursery, and hoped that would help. She still doesn't say mum, ta, yes or no. infact the only words she does say is "dat" (whats that?) missy (our cat) woof woof (for dog). she also makes the sounds for counting 1 to 10. I'm worried I should be doing more to help her development but with no family support I have no way of asking others advice. She is also throwing BIG temper tantrums which is hard to bare so i put her in her room until she calms down. is that right? she still naps during the day but only when i put her in her cot otherwise she screams because she's so tired. Please help???