Jennifer Lopez kept things cool Saturday night while attending Ariana Grande 's "Eternal Sunshine" concert in L.A. ... but even a low-key night out didn’t stop fans from spotting her among the crowd. TMZ obtained video of JLo inside the crowd, fully in vibe mode as she enjoyed the show from her V.I.P. seat. However JLo wasn’t drawing attention to herself -- no big entrance, no theatrics -- just blending in and taking in the performance like everyone else. At moments in the clip, she appears