I have read your posts...and did remember it was Depakote she was on.
Ok, gonna be my lovely blunt self here with ya k? She's your W, her meds are affecting your R. You DO have the right to interfere. Personally, I think you are placing too much assumption as to the "why" she didn't tell you about the Dr's appt. You are assuming she didn't want you there...did you ask her? If you didn't, don't assume it.
I believe you truly need to have some clear communications with her...I see you tiptoeing and that's not productive. I can certainly understand her trepidation about altering the doseage, that could be scary for her...she probably has valid fears that you won't like her suddenly if her moods change while you guys figure out her proper doseage. That's why you need to sit down and have a "no bull" conversation...a loving/supportive one....but you need to be assertive too "this needs to be done."
You getting involved in her mental/physical welfare when it's obvious there could be an outside source affecting her and your R isn't disrespectful....I repeat, it's not disrespectful. Would you let her remain over sedated by a prescription of valium or morphine? While it's true those two items are addictive and Depakote isn't....it's not much different....she's over-sedated and it's affecting her well-being and your R. It is not disrespectful to say "Honey, I don't like how this is obviously making you feel, I know you are worried about changing the doseage but I promise I'll be here to help you through this til we get it right."
I'm going to repeat what I said to you in my other post. The drugs are affecting her behavior, her mood, her motiviation.....she's not likely to do this on her own as you've said. So....right there's a boundary/consequence you can set. "In order to show me that you take me and our R seriously I'd like for "us" to go talk to your Dr. about adjusting your meds, I will be happy to make the appt. if you'd like".