Hi, it's me again. I spoke to one of the two directors, Nathan Greno, on Facebook, and he said it depends on who I ask. He said others felt it was the last drop. Here's what I wrote and what he wrote me (his message is the red):
Hi, I'm Kristi. I would like to ask if Rapunzel's tear was the last drop of the flower's magic? Some fans think so, and I don't, because her healing ability was in her hair, and if it went down to her teardrop, I believe that it could be used from elsewhere inside her, just like it did for her hair and tear. Yet, they (at least one person, which makes me think there are other fans who believe that) find it impossible. So I'd like to know the answer from you.
To be completely honest, it depends on who you ask! I think that magic is still inside her, but other people on the crew felt the tear was the last drop. I'm not sure why the power would run out? If she would have kept her hair, I feel the power would have lasted her entire life. In other words, I agree with you!
I can screenshot the webpage if you think I made up the message above.