The Crown and Rapunzel's Virginity
For the beginning of Tangled, we have a pretty standard MacGuffin in the crown that Flynn steals from the castle with the Stabbington twins. The theft of it and his subsequent escape from the palace guards are the reason why Flynn stumbles upon Rapunzel. Rapunzel uses the crown to force Flynn to escort her to the palace. Not to mention that Flynns betrayal of the Stabbingtons so that he could escape and have the crown to himself is the reason why they hate him. When Mother sees the crown later and deduces that Flynn is with Rapunzel, it stops being a MacGuffin, but until then it functions as a fairly average one. However the crown is not simply a MacGuffin; it is a symbol for Rapunzels virginity.
First, it is important to know that technically Rapunzel has had the crown since birth. After all, as the daughter of the king and queen, the princesss crown is hers by birthright. It is something that she wholly owns. However, she didnt always know it was hers because she was kidnapped. She only begins to figure this out later when she goes out into the world and learns more about it and herself. This is not unlike a girls virginity. It is something she is born with and that she owns. However, many girls dont know what it is until they are older and begin to learn about their bodies and the world around them.
Second, consider Mother Gothels words to Rapunzel once she finds Rapunzel the first time. Mother Gothel tells Rapunzel that as a mother, she knows that once Rapunzel gives Flynn the crown he will not want to be with her anymore. She says that Flynn doesnt really like her and that he is only sticking around, waiting for Rapunzel to give him the crown; once he has it, he will leave her. If you replace crown with virginity, you get the same advice that nearly every mother tells her daughter(s). Mothers tend to warn their daughters to save themselves for the one they love and warn them of those that will just use them until they get what they want, i.e. sex.
Third, there is the fact that in the original Grimm version of this story, Rapunzel does give her prince her virginity, leading to a teen pregnancy. This idea of the crown being a symbol for virginity would make sense since by the end of the film, Rapunzel does end up giving Flynn the crown.
It would also make that scene that much more significant and heartbreaking. In this scene, Rapunzel tells Flynn that she was afraid, but now she wasnt and then gives him the crown. Then when Rapunzel thinks that Flynn took the crown and left, she is devastated to the point that she willingly goes back home with her manipulative and cruel mother. If we equate the crown with Rapunzels virginity, then her giving it to Flynn becomes a sexual act: she is giving him her virginity. She is no longer scared because she trusts him. Then when she believes that he has left her, Rapunzels devastation is now a product of the real life fear that many girls have: trusting a guy with her virginity and having him basically spit and trample all over that trust. Traumatizing, indeed.
The Hair and other sexuality symbolism
In addition to the crown-virginity theory, Rapunzel's hair can also represent awakening sexuality, or more generally turning from a child into an adult. While the hair is light, long and magical, she's a girl, not developed into a woman yet (also meaningful because lighter hair tends to go together with youthfulness: many light-haired children naturally develop into much darker-haired adults).
During the "Kingdom" scenes, it is braided for what we can assume the first time in her life, making it much shorter. This is accompanied with dancing with other people for the first time (with an ecstatic look on her face at the end of the "Kingdom Dance" song), and her and Flynn's first starting to realize their romantic feelings for each other.
Mother Gothel pointedly unbraids the hair upon their return to the tower; like a parent having difficulty accepting a child growing up, especially the developing sexual maturity side of it.
Then it gets cut into short and brown: fully sexual awakening.
Also, "the chalice and the blade" are symbols for femininity / the woman (plus the element of water), vs. masculinity / the male (in pagan rituals a blade was sometimes dipped in a chalice full of water or wine to symbolize a union of the masculine with the feminine, in a sense that could range from metaphorical to the physical sense). The tear symbolizes "the chalice" (being of water, coming from Rapunzel, and being healing) and the mirror shard that cuts the hair is "the blade" (literally used as one).