Teen Mom 3's Mackenzie Douthit may have a baby son at home, but she's just like any regular high schooler and she fully intends on having a magical prom night. The only problem? The dress she wants is $200! Should she splurge or save her cash for little Gannon's diapers? Check out the sneak peek and tell us what you think in the comments below! Teen Mom 3 airs on Monday, September 9 at 10 p.m. ET on MTV.