D.W.
It's easy to tell someone not to live in fear, but when you're the one who's gone through it, it's a completely different story. Febrile convulsions/seizures are scary - especially when you don't know what triggers the fever to set-off the event.
I might recommend starting slowly to introduce her to her room to help make the transition easier for all of you.
Initially, I'd put her in the bed and perhaps have either you or DH sleep in the room with her (~1 week). Then, move to staying every other night or long enough for her to fall asleep and for you to feel safe.
I'd recommend keeping the door open and putting a baby monitor in. If you can find a used video monitor via eBay, Craig's List, etc. that might help vs. the cost of something new.
This next suggestion is going to sound so silly - but do you have pets? Especially dogs have a 6th sense we don't have and are known to alert people when there's a health issue for a family member. My in-laws inherited a canine companion who'd been trained to assist a man with epileptic seizures. It may help provide you peace of mind, and it may be something that there's assistance with to cover costs if it really is a valid health issue.
Good luck!