They understand SO much - I'd say pretty much everything, although double barrel instructions might be a bit much right now. Understanding and following are a whole different issue though! I'd say this is way too early to be prompting her to say ta - as LZ says, role modelling is the way forward - if you say your pleases and thankyous to her, and you and your partner say them to each other, and both of you say them to everyone else around you, she will learn that it is the right thing to do. Practise it, with toys and things - if she hands you something (especially play cooking) make sure that you say it then. Children learn far better during play than during any other time.

TBH, "ta for mummy" has never made sense to me. I would rather say "Can you please give that to me?" because then you are role modelling an appropriate sentence.

Congrats on making it through your first year!