My brother US citizen applied for a Fiancee visa and within 3 months his wife to be came here. They had 90 days from her date of entry to get married. They got married here after a month, and applied for her GC and she got the GC after 4 months she applied. The only interview she did was at the embassy.
If you marry her in Greece, then you have to wait for the processing time here in USA which is much longer up to a year or so. Good Luck.

