I had experiences where dream characters behave differently from their waking counterparts. I guess it's just the way our subconscious conforms to our lucid awareness. However, I have had non-lucids in which family and friends had behaved differently too. Dream reality can be a bit quirky. I guess the best you can do is to think of the dream character as part of your friend, that way the dream character will behave more along how you know her to be. It could also be that subconsciously you might be feeling like she may have changed a lot and this line of thought might be manifesting in your dreams.

Only person that's consistent for me is my departed significant other. She behaves in her familiar way whether it's a dream character of her or if she embodies her dream character to interact with me.