Could i applied De Facto visa with my girlfriend in australia?

De facto partners are allowed to pursue permanent residency in Australia. You must have this type of relationship (same as de jure, common law) for at least 12 months preceding the date of sponsorship. Since you have lived together in Mount Cook Village from Feb. 2007 to Jan. 2008 (11 months) and practically lived together for another 3 months (meeting your family and traveling) plus living together in Australia till Aug. 2009, you appear to have the requisite period of relationship. You can be sponsored then as a de facto partner. The following link shoudl provide you with official and complete information for this process. www.immi.gov.au. When there, click on the links relatd to Migrants, then Family Members. The options would be presented to you.