I want her to eat my cum

Count yourself lucky she sucks your dick and let it go.

Well, firstly, cum is liquid - so, Drink (not eat). Secondly, if you want her to drink your cum, then you'll need to be more erotic during sex, because it is her choice... and if you are kinky and willing, then she'll be too. But, ultimately, it's her choice - not yours. If you want more from her, then she'll need more from you.

A woman who wants to really satisfy her man will swallow every drop of his cum.

Bro you were supposes to insure this before marriage. All you can do is perhaps look up some articles she can read to learn about its importance to men, and maybe exchange with what she would like. Yes all women should do this. But this is who she is and you can't date or marry and expect positive change.

Will you eat your own semen?

Three things that seem pretty stupid to me:

1) Guys who want women to give them oral, but won't give it.

2) Guys who expect women to gulp down their jizz like it's ambrosia, but freak out at the idea of tasting something their own body has produced.

3) Women who are happy to suck a guy off to orgasm (kudos for that bit), but then spit out the semen. I mean, it's in their mouth already. If they don't like the taste, swallowing is not going to get rid of that any faster.

Assuming you give your wife oral, the next time you finish with that element of your love-making, start spitting into a tissue and going through whatever routine she does after sucking you off. Ask her how that makes her feel.

Or, if you don't like the idea of a sudden cessation of all sex, you could just put that hypothetical situation to her at a non-sexy moment.

As for why some women won't do this, reasons vary. Some women don't like the taste (but, like I said...). Some women don't like the idea that they'd be swallowing millions of little squirmy things. Some women have problems with the idea that they'd be swallowing something that comes from the same place as urine.

Only your wife can explain why she won't do it.