Captain is conveniently defining away the label. That is, presupposing bubblegum pop can't have some lyrical depth. This disussion likely won't go anywhere without a consesus definition of "bubblegum," "pop," and "depth."

With that said:

-writing about a marital breakup isn't necessarily "deep." Feelings or emotions over a "boy" can be equally genuine and revealing.

-clever lyrics can still be poppy. The song "Rush Hour" by Jane Wiedlin reminds me of a song that's completely and totally bubblegum pop but is actually very clever. Most of glam metal had very clever lyrics (double entendres, etc.) and is very pop.

-Avril Lavigne probably writes deeper lyrics than Katy Perry but Avril's still bubblegum pop - she the quintessential pop act (common time, big choruses, catchy melodies, short songs, songs that girls can relate to, et al).