Jennifer Aniston has sparked engagement rumours after showing off a glitzy rock on her ring finger while attending the SAG Awards on Saturday 24 February at Los Angeles' Shrine Auditorium & Expo Hall.The actress, 55, was a vision in a glimmering silver gown, which featured a thigh-grazing slit and low neckline. However, attention quickly turned to her choice of jewellery, and what looked like an engagement ring on her left hand.