Bringing girlfriend to daughter's school event - bad move?

Been dating Sarah for about 8 months now. My 12yo daughter knows her, they get along okay, but nothing serious yet. School is doing a thing where parents come watch presentations. Ex will definitely be there. Sarah asked if she could come and honestly I'm torn. Part of me says it's normal, part of me worries it'll upset my daughter or ex will make a scene. What's the vibe here? Too soon?