One of the things that I find hard to describe about talking to Heidi is the gaps in conversations. The pauses you have to leave so she has time to process what you have said. You can see / hear it a bit in these two videos.
Some concepts are easier than others to process. At times if there is less sensory disturbance around Heidi will absorb what you are saying much faster.
Other times what you are saying is of such huge import that it takes longer to process. When a much loved friend of ours told the girls she was pregnant, Annie responded with “Congratulations”, Heidi overwhelmed by this huge news, but knowing something was required of her, screamed joyfully “banana”… then bounced all over the place, her body language communicating her joy in the news far more effectively than her words.
Recently we had to break the devastating news to the girls that Oz The Cat had passed away. We waited until the Saturday morning to tell them, working on the premise that timing the news when we were all at our best was a good idea. Annie was broken hearted, she had a million questions and so many tears. Heidi was sad that Annie was sad, gave her sister a hug and told her “Banana”…. then wandered off to sing disco songs and dance in her bedroom.
Nothing more was heard about it from Heidi, until Tuesday of the following week. We were getting ready for school, her Dad and I helping Heidi with those pesky shoelaces. Heidi’s eyed filled with tears and she looked at us “Oz da Cat is dead”. It had finally processed 
I suppose what I’m trying to say is that you might not always get the socially appropriate reaction, not straight away. And be careful not to overwhelm with your words, think about what you are saying and try to observe how it is being absorbed.
