A few scattered thoughts on this one - I was trying out these little breath bubbles and I think I might've gone a little big with them here. They end up looking like empty word balloons. They did end up causing confusion throughout the time I was using them (from recently until the end) but I needed nonverbal ways for the characters to express things, as the tone of OP got increasingly visceral and less schticky.
I don't think I need to speak on the topic they're discussing, other than that it's a phase Jane is beginning to emerge from, and Mar has just recently exited. This is the first in an ongoing series of ways that Jane & Mar help each other cope with life. And while that's inseparable from the romantic connection, I don't think this is the actual spark that ignites them. Just a realization that they're both adults, and that they're awakening to certain freedoms.
Of course those freedoms come with the responsibility to realize and shed destructive habits - also an ongoing struggle for them.