Brianna Aguilera masked any struggles or dark thoughts she had in the months leading up to her death ... as newly surfaced photos show her beaming widely with her boyfriend on Halloween.

The 19-year-old college student dressed up as Glinda from "Wicked" -- complete with blonde wig, pink gown and massive tiara -- while she posed next to a guy in a green jacket covered in a leafy gold pattern like Fiyero wears in "Wicked: For Good."

Aguilera and the guy -- who Daily Mail reports is 20-year-old Aldo Sanchez , Brianna's boyfriend -- are grinning ear-to-ear in the pics and clutching each other tightly. Instagram / @brie.aguilera

The couple posed in a number of pics together over the past year ... including one particularly eye-catching shot from August when Aldo plated a note at

See Full Page