Hope they will fix it soon. I don't want to remove and readd the relationship everytime I travel/manage world. I'm not enjoying it. So I don't play it until this Bug is gone. With the Side Effect that I'm not purchasing any additional Content until it's fixed.
It seems that this bug appears after you switched to "manage Worlds". I created 2 new Sims (Teen Girls), they could make friends without problems. After I switched to manage Worlds, The relationship changed to neutral and I can chat up infinitely, without any change.