Yes the bubbles are hand drawn, and they are very simple to do. Just make a new layer, pick whatever area color your drawing is (in my case greenish blue because of the walls), set your brush to low opacity,
draw a circle with that color, mix alittle bit of different color if you want( I added some purple), don't color the whole circle though cause you want to be able to see through the bubbles clearly,
then pick white and set your brush to high opacity and color in white on appropriate area (see my picture on where I colored white or search for your own reference.)
Oh, lol, sorry. The picture's done digitally. Because eventhough it was done digitally, it was regularly drawn just like you would on paper with no special effects(it doesn't even have to be done on a new layer, I made a new layer just so I can copy and paste some because I was lazy ), I would imagine it should be the same concept doing it traditionally though.
Softly draw a circle on top of your picture with whatever area color your picture is, then apply some white ink, white ink pen, or white whatever depending on what media you use. The only difference is you will have to be very careful not to mess up doing it traditionally, that's all.
Oh yes, she's has been on my watch list for a while as well! I go wow and stay the longest at her table whenever I walk around the alley. Beautiful drawings. This artist(that you probably already know of) does awesome watercolor and copics as well, she also does mangas