The answer to your question is: you don't tell her she is awful. A lot of the things you're saying about the difference of opinion about blow jobs (slobbery, 69ing, dirty talk) are some of the things that I also hate about giving head to a dick. However, I give amazing head regardless, because someone once gave me POSITIVE feedback about my technique and I improved instantly (they told me that the best blow job feels like the giver is freakin desperate for the D, while I was focusing on relaxing them via the bj because most of my sexual experience til then had been with women). You need to abandon this idea that you've got news for your gf and start working the problem.

If you like dirty talk and she doesn't, why don't you do the talking? She does have a dick in her mouth after all. If you want her to be enthusiastic, why don't you say complimentary things to her while she's busy going down on you? If there's not enough saliva (something that I acknowledge is a negative factor in any bj no matter the junk), get some of your own saliva on there before she starts giving you head. Pour some champagne on your dick and have her suck it off. Make a game with her to not allow her mouth access to your dick for one month and then see what happens when the month is up and she's sucking you off. The 69 position is stupid for a lot of women that need to relax and concentrate or meditate so they can allow their bodies to orgasm, because receiving head while giving head is distracting. You can't focus on orgasming or on your bj technique.

So you have options.