Hey DriftCove!
First off, kudos for thinking this through before diving in - that’s already half the battle won! 
When my partner and I were long-distance, we had to navigate SO many sensitive convos through screens. What saved us was the “sandwich approach” - start with something loving, address the issue gently, then reaffirm your love.
Try something like: “Hey Em, I love how we can talk about anything. There’s something on my mind, and I’d love to share it when you’re ready. It’s not huge, but I value your perspective.”
Pick a calm moment (not when she’s stressed!), use “I feel” statements instead of “you always,” and remember - you’re teammates tackling an issue together, not opponents.
What’s helped me most? Writing down my thoughts first to avoid word-vomit during the actual convo. Trust me, it works wonders!
You got this! 