Any where the female lead and male lead are in love, but circumstances causes her to marry someone else at first? She doesn't go through with it and then gets together with the male lead.

I couldn't think of a drama that fit your description 100%, but these are pretty close. hope this helps... ;-)

Another Miss Oh (engaged to a guy, then breaks off engagement for main guy)
Reply 1988 (this may fit your requirements depending on who you view as the male lead)
Say you love me
Que sera sera
but in both they married another guy... 
@Totoro 

Well all 4 guys are prominent so its one of those with the multiple male leads stories.
Scarlet Heart: Ryeo,
Female lead is in love with another character at first, they promise to marry each other if he gives up his greediness > circumstances led to her not marrying him and falling in love with the male lead. This is maybe what you are looking for?

Duangjai Akkannee
Female lead and male lead develop feelings for each other despite knowing that their families will not agree to their relationship > female lead father keep pushing another guy in her life and wants her to marry him > she does not like him and some things happened that made her relationship with the male lead possible.

Sarm Noom Nuer Tong
Well there are actually 3 female leads and 3 male leads in this drama, but 1 female lead has a boyfriend and is super faithful to him while her boyfriend is really abusive and likes to sleep around. Male lead keeps liking her and his friends ( the 2 other male leads ) try to find opportunities to get these two together. The female lead was not married or was planning to marry tho.. I think, I don't remember it anymore.

Ton Rak Rim Rua

This drama is a bit different then your description tho. The female lead was already married to the male lead because of a request, divorced, married again because of work problems, I don't remember if they divorced again and married for the 3rd time later on or that they never divorced after the 2nd marriage. But after the 2nd marriage female lead began to like a coworker > was planning on marrying him > changed her mind and came back to male lead.

The last 3 are thai drama's and the first one is a korean drama. I hope that my recommendations are the types you are looking for~
Biscuit teacher and star candy - this totally is the drama you are looking for. She already has her white wedding gown and everything was prepared. But she didnt go through with it cause she loved another. 

lovers in prague - also what you are looking for, the wedding hall is already prepared, the female is in her wedding dress but she doesnt go through with it since she loves another and she is just being blsckmailed to the marriage

new tales of a gisaeng - not really legally marry, but close enoigh since its a gisaeng marriage thing. They go through the process of the gisaeng marriage, until the last possible memoment it is all is stopped

A love to kill - not really marry but close enough. She choose the other guy who is the male leads brother and also she did love him before and she also feels guilty toward the first guy