the first time it shows up framed as an actual version of the myth is in the 1970s from a book called “Lost Goddesses of Early Greece” by Charlene Spretnak. Spretnak does not cite any sources.

All ancient sources (Homeric Hymn, Apollodorus, Diodorus Siculus, even Ovid) have her taken unwillingly and tricked/forced into consuming the pomegranate seeds.

She does, ultimately, come to love Hades, as evidenced by other myths, but she never chooses to stay in the first place.

Alongside being a myth about the seasons changing, it would also be relatable to mothers and daughters in ancient Greece. Because daughters were essentially property of their fathers, neither they nor the mother had true legal control over who she would marry. I'm sure that there were plenty of men who did care about the wishes of their wives and daughters, but there was really no recourse if someone decided "Hey, we're marrying you off to this older man."

So, it's also a myth about marriage. In the Homeric Hymn to Demeter, Helios tells Demeter that she should be happy that, out of all the people Zeus gave Persephone to, he chose someone so very rich and well respected. Persephone is frightened and distressed in the underworld, but later learns that it's not all that bad, and she enjoys an immense amount of power and respect. So, Greeks are told

• Your new husband may seem scary, but with time you will grow to accept and enjoy your role as a wife.
• You may be sad about the loss of your daughter, but she will be much more fortunate with a good husband.
• You can decide unilaterally to give your daughter to someone, but things go much more smoothly if your wife is consulted about it beforehand.