Eh, if I had a child, rather have child MTB than road. I feel safer in the woods and trails than on the road. Texting drivers scare me more than any tree, rock, cliff, steep hill etc. But I enjoy the speed of the road bike more. Not criticizing any parent's choice here, just saying I'd rather have hypothetical child enjoying the trails rather than the road.
I modified an adult folding bike into a 7 speed mtb. Put slicks on it, replaced the crappygrip shifter with an indexed thumb shifter, stripped and painted the frame, mounted the stem backward to give her ideal reach. Two years.later I'm seeing more seatpost and stem but she is riding like a pro. Runs 20 inch wheels so its pretty fast. :)
I added some pics of my son's Felt F24.
It's got 24 inch wheels (23mm) and 24 inch standover.
Here it is compared to my 61cm Allez.
It's Sora brifters and FD. Tiagra RD (8sp).
Pinarello FP 0 Kid's Complete Bike | Competitive Cyclist) earlier this year for $500 for a bike I bought for about $700. She rode good 3 years with it, so it was well worth the money for us.
Before that, I went through similar thoughts of upgrade to a kids bike, and actually did put a pair of slicks on it, but as soon as we got her the little road bike, the speed difference is night and day. So I would highly recommend getting a real kids road bike if you think your daughter is actually going to ride a lot.
I've seen the Fuji ACE bikes in person and they don't look/seem terrible. The only thing I think is crappy about them is the stem shifters, but understandably no one makes a really good kid sized STI shifter.
you can also try and find a local dealer for isla bikes (High quality lightweight children?s bikes from Islabikes) as they're kid centric from the get go.
otherwise find a super small WSD and see if you can make it work.
found a bunch of 20" road bikes in the uk all boys but I cant find a 20" girls road bike. it cant be a 24" my daughter is only 7. anyone know of any please let me know, new or used is ok. me and my daughter just rode 30 miles last week, but a little slow on her mountain bike. she can do distance but her bike is slowing her down. she can ride her unicycle over a mile too. I guess if its a boys bike with the top bar it should be ok too. I'm only finding them in the uk though, and shipping would be crazy.
Found one!!!!! A 20" road bike stand over height is 22" and it's complete and ready to go. It's a pinnacle 5 speed, think it's made in the uk from the 80's