The context of the following conversation is Kendall wanted to have a great birthday party for her friend so she bought the cake.:
Kendall says I am throwing a birthday party for my friend..
The friend responds That's nice of you. Is it a surprise party?.
Kendall responds No, she knows about it. She wanted to keep it low cost..
The friend responds Why, is she is paying for it herself?.
Kendall responds I don't want her to.  I really want it to be very nice, so I got a really good cake..
The friend responds This is very nice of you..