Was J. Lo throwing Mariah Carey major shade during last night's (May 17) Billboard Music Awards? As we previously noted, Jennifer Lopez’s reaction to Mariah Carey’s “Infinity” performance at yesterday's Billboards was… begrudged to say the least.

Carey delivered a solid rendition of her latest single while powering through a bad case of bronchitis. Needless to say, the celebrity-lined front row -- including Taylor Swift and company -- gave it up for Mimi’s Billboard performance, which just so happened to be her first in more than 15 years. Everyone, that is, except for J. Lo, who kind of grimaced as she reluctantly clapped after Carey concluded the song. Now, we’ve learned that not only did J. Lo look less than impressed, she apparently spent much of Carey’s performance scanning her phone and chatting up Casper Smart.

In a video, TMZ points out that J. Lo can be seen more focused on her phone than on her fellow one-time American Idol judge’s performance. However, when a cameraman comes into frame, J. Lo puts away her phone and kind of bobs her head along with Carey's new tune, and as we already know, eventually shows some rather strained appreciation for the "Infinity" singer’s larger-than-life singing chops.

Regardless of J. Lo’s reaction -- or lack thereof -- Carey followed up the Billboards by treating her fans to a super-short teaser of her upcoming “Infinity” music video. Even in a mere 30 seconds, Care manages to pack the clip chock full of glamor -- as if we would expect anything less from the pop diva.

See J. Lo and More Celebrities Without Makeup