I'm surprised by the responses related to one's own cum. Guys really won't kiss their significant others after cumming in their mouth? Seems a little strange that you feel it is ok for her to take it but you are then repulsed by the very same mouth that gave you that pleasure?
Do guys expect their significant others to demand a mouth washing after they perform oral sex on them?
Man, when it comes to the bedroom, we don't have any hang-ups. Juices are passed back and forth constantly.
As for play partners, there hasn't been a situation where she has taken another man's cum in her mouth but I wouldn't avoid kissing her. Why would I give any impression that my significant other is not gross and needs to be cleaned before I kissed her?