The biggest thing I have found is that often it's not actually about the taste. It's the barriers in the mind affecting the perception of taste. Yes, it tastes different than beef because it's a different animal. My wife was the same way for quite a while because growing up, if she had venison, it was prepared poorly and she did not enjoy it. It has taken her a while, but now is ecstatic anytime I bring home an animal because she has changed that perception in her mind and gotten used to the difference in taste.
In terms of preparation, I don't want to entrust a processor with my meat. It's not that there aren't good processor's out there and you may have a really great one, but if I do the processing myself, I can control everything from beginning to end. I take my time with it, make sure it's on ice, clean it thoroughly, trim anything that may give an off taste, and package it appropriately for long-standing in the freezer. By doing this, I have eliminated the majority of factors that contribute to 'gaminess'.
The next piece of advice is to really begin to read and consume info on wild game cooking. Know what parts are best used for what styles of preparation (slow cooking, fast cooking, adding liquid, etc.). This has been a game changer for me. I know longer have dried roasts because I use the correct roasts for slow cooking. My steaks are tender because I use the correct parts for steaks.
I have found certain seasonings play better, but typically if you use a mix of something with vinegar and something sweet, you will end up with a pretty tasty result (think honey mustard). Also, tomatoes are the greatest ingredient to use with venison in my opinion. You can use them in so many ways (canned, paste, sauce, ketchup, bbq sauce, fresh salsa). It has a ton of advantages and. Irarely prepare my venison without some aspect of it having tomatoes.
Just my thoughts. Hopefully over time your wife will see your passion about the quality of meat and food you are preparing and will acclimate to it. It's worked for me and my wife. Hopefully it works for you too. Good luck!