The state of being honestly, sincerely happy for someone else's good fortune--so happy that you could squee--yet also feeling just a little envious of it at the same time; an ambiguous feeling of excitement and envy. Root words, squee + envy.
Also includes: squeeenvious, squeeenvied.
"I'm feeling a touch of squeeenvy right now; my brother won tickets for a cruise ship, but he's taking Mom, not me!"
"When I heard she got a date with that cute guy behind the counter, I was totally squeeenvious of her good fortune. He wouldn't go out with me, but I am glad he's going out with her!"