I have 2 daughters who ride Surly LHTs . One is 5' tall, and rides a 42 cm; the other is 5' 5" and rides a 50 cm frame. My wife is 5'3" and rides a custom built 47 cm, and I know this one fits perfectly. The difference between the 46 and 50 cm bikes is only 1.5". LHTs has a longer top tube compared to most bikes, which increases the reach. I ride a LHT and found that I had to use a shorter stem than my other 58 cm bikes to get the same reach. This is a plus in your case. What are the size of the spacers below your stem? Do you have any steerer tube left above the stem? What length stems are on your other bikes?
I'm just making a guess using the the information you gave, and my experience with my family. IMO, if the bike feels too small for you , it probably is. If there is no steering tube left above the stem to raise the bars level with the saddle without using an extender, it is probably too small. Hopefully, you will get other opinions that may help. It sounds like you already know that fit is the most important thing.
Both daughters rode their Mom's 50 cm road bike and her older 50 cm touring bike without any issues.
The 42 cm bike is first, the 47 cm bike second, and the 50 cm bike is last. The five-footer on the front bike has a 17 degree short stem, 50-60 mm. I think she could use a longer stem and less angle, but she likes it and has ridden it that way for several thousand miles. When I cut the steering tube for her, I left 10 cm above the stem just in case she changes her mind.
Fifty cm frame with 5'5" rider. She is on top of the bars, and this seems like a good fit. Her seat height , and saddle/knee were positioned,and stem length determined for her desired reach.
This is how the 50 cm bike is set up for a 5' 5" rider with long legs and arms. There is not a lot of seat post showing (about 4"), and the seat is close to level with the bars.
