Poor baby. Can you put Lucy in a separate container in your brooder so she can see the other chicks and they can see her for a few days? Warmth will be important since she is by herself but hopefully in a day or two they will accept one another. The important thing is that she not get picked on to the point that they do her any real harm. Their pecking order can be a bit hard to witness. Lucy might always be at the bottom of the pecking order but you can never tell.
As for being sad about unexpected roosters, let me tell you about our boys. We bought 8 Buff O pullets and two cockerels along with 4 Welsummer pullets. From the start we recognized our two Buff O boys, then we noticed something. One of the pullets was growing faster than the others and at 6 weeks grew a bodacious set of wattles and comb. Yep, she was a he and a big he at that. Then wen discovered that two of our Wellie 'pullets' weren't going to be doing any egg laying any time during their lives. Suddenly my two rooster flock was up to 5 roosters and 7 pullets. Good Grief. I knew I was going to have to get rid of at least two of the roosters. But which two. I immediately noticed that the two Buff boys who were supposed to be boys had a decidedly mean streak to them. The 'surprise' Buff rooster could keep them in line but they had the nasty habit of trying to kill the Welsummer roosters who had developed into really sweet boys who were great with the hens. So after getting beat up myself a few times by the two bad boys I passed them onto an Amish neighbor for breeding and Sunday dinner. At that point I had one really fantastic Buff O rooster named Fred the Red or Red for short and the two Welsummer boys, Bo short for BOHICA and Chester named after the character on Gunsmoke that had a bad knee. Chester got hurt in one of his tussles with the two bad boy Buff O's that left him with a bowed leg. In spite of handicap, he has risen to Apha male with Red his sergeant at arms. Now in the meantime, I got a young Lavender Orpington pullet and guess what! She was a he also but hen or rooster, I wanted a LO in the flock so I looked at my 4 boys and the flock of hens which is now up to 12, told them to work it out among themselves and walked away.
The flock is a year old now. I have a broody hen sitting on a pile of eggs, Chester is still gimping about with Red following him around leading the hens who seem to prefer him over Chester even though Chester is Alpha. and finally, Bo and Larry (started out as Lily but you cannot call a junior rooster Lily. The other boys will just beat him up worse) who stay on the outer edge of the flock trying to impress the girls. Was I sad when I learned about my influx of roosters. Well, yeah. But I tell you, I love our boys dearly. The hens are sweet and funny but the boys have the charm and personalities. I know I will have to part with any cockerels spring hatchings produce and yes, as much as I would like to, I know we cannot keep them all.
I sure hope your Lucy settles in ok and I hope you can find a way to keep your potential boy. If you can you will never regret it.