Anongoodnurse's answer is spot on, but I wanted to add a couple of things.
First off, don't forget we as humans are amazing at pattern recognition, to the point that we see it where it doesn't belong. You'll hear her 'say' lots of things that seem like perfect words, once, but not again - because she didn't really say it, she just made a sound that your brain converted to a proper word. (This is why we can understand people talking, much of the time - you probably only really get half to two-thirds of what's said, but your brain figures out the rest. This is why Telephone is a fun game.)
Second, don't get too hung up on exactly what the word sounds like. It's very common for a child to be able to understand the concept of a word before being able to pronounce the sounds for that word. Especially at 12 months, which is still fairly early in the 'talking' spectrum, she may well understand there is a word 'mom', but not be able to say 'm' - so she says 'da' instead. Or, she uses 'da' to mean 'parent'. My seventeen month old can say a lot of words (15-20), but still often defaults to 'da' (his first real one) for things he can't pronounce - he points to them and says 'da', or sometimes he uses it for verbs he doesn't know. But it's clearly an attempt to communicate, and it often works. To me that's the more important aspect of things: the attempt to communicate, not whether it actually sounds remotely close to the word.
Finally; I wouldn't worry too much about defining 'talking' in any meaningful sense, unless she's over two and still not clearly talking. A lot of these things we as parents want to check off a box for 'does my child do X', but it's not that simple, and it's not really that important, either.