O que significa "Dress to wed'' (Nome de filme)?

“Vestida pra casar.”

Wed and marry can be synonyms.
As verbs ”marry” is related to marriage or the matrimony and the term “wed” is about the ceremony where bride and groom take each other as spouses.

To sum up:
Marry = casar
Marriage = casamento

Wed = casar **
Wedding = casamento **

** mas nesse caso e no contexto apresentado, casar é a cerimônia em particular, “vestida para se casar” seria uma boa versão para a ideia do cerimonial do casamento.

My point of view ok. Wait for more replies please.

Let´s think of "marriage" and "wedding", it makes it easier to understand the reasoning.
Wedding it at the day, and marriage is for life or till death do them apart, or till decide they have irreconcilable differences, etc.

The rest was taken care of and clarified by Cinnamon, as always in spotless way.

In addition to that information "dressed to kill" means wearing fancy and attractive knockout clothes.
So, "dressed to wed" might mean wearing fashionable clothes, ready to go on the prowl at the party, etc. Wow!

Now, taken literally it would be "vestida pra casar", wearing the dress to the wedding day. It´s a common expression with stores that sells wedding gowns.

In the movies field, there is a film "dressed to kill" that depicts a cross-dresser transgender turned into a psycho, it turnes out that there´s a 'Jekyll and Hyde' alter ego thing going on.

https://en.wikipedia.org/wiki/Dressed_t ... 1980_film)

That somehow reminded me of the "Noivas de Copacabana" movie, but the similarities stop at the psycho thing.
The latter film was about a guy that was a car mechanic and separated from his wife, somehow he took pleasure to preying and killing his victims by attracting them and making them wear wedding gowns. Real creepy!
The TV made it into a fictitious history of an antique art restorer, but with the same psychological traits, and the similar plot.