Tilley's inswinging cross six minutes into the second half deceived Rovers goalkeeper Andrew Fisher and flew into the top corner.
Blackburn had led on six minutes, Joe Nuttall scoring his ninth PL2 goal of the season but Brighton's Beram Kayal marked his comeback from injury with a goal three minutes later.
Nuttall chipped Tim Krul soon afterwards to restore Blackburn's lead before midfielder Willem Tomlinson was sent off just before half-time.
Blackburn drop to third while Brighton stay in eighth place.
Both teams are back in action on Friday with Brighton entertaining Middlesbrough at the Seagulls' Performance Centre at lunchtime and Rovers travelling to face Newcastle United at the Northumberland FA in the evening.