First timer

My girlfriend and I already role-play mommy/daughter, I am thinking about asking her to diaper me after an enema series. Any advice in how to go about asking her?

You could get a diaper, and have it sitting out. Let her ask about why it's there, then you can indicate you would like to be diapered. This way, it will almost be like her asking you.

Tell her having enemas makes you feel like wearing a diaper afterwards, & would mommy do the honors

You have two solutions : or you tell her you like to wear diapers, or you buy diapers directly and show her that you like to wear diapers :-)

It depend on your wife.

If you play mommy/daughter and used to get enemated, normally there won't be a problem to diaper you.

But you should not evacuate your enema in your diaper especially the first time. You may be disapointed.

You ca wet them, it's the easiest way to go further. Poo in diapers is especialy smelly and sticky.

After the thicker the better and try to choose plastic backed diapers.

Since this question of yours is from about 2 years ago, I'm curious if you have asked her yet. I think it's neat that you are bi and I hope you gals will have a nice future sharing each other's fettishes and loving each other.