After a bit of research, it's certainly not unlikely for her to get a splint at 18 years old. I talked to my vet, and he said the same, and that she could have burst a blood vessel when she smacked herself with the branch. He suggested cold-hosing or icing the first 36 to 48 hours, and Bute if I had any [I don't]. He said as long as the cut [which is very shallow and miniscule] isn't deep or gets infected, she should be fine after a month, and that she should be rested for about 30 days. He also said that if she is still lame in two or three weeks, it should be x-rayed for a fracture.
She is lame, but just barely. It is warm, and painful, all of which I told the vet. She's in her stall with standing wraps, she's been cold-hosed or iced a total of two hours in the last 36 hours [10 minutes on, 10 minutes off] and is certainly in good spirits.
I know splints are far from the worst thing, and that lots of horses have them. I just wanted to verify all the information I have, as well as make sure I'm doing good, or if there's something I forgot. Thanks. =]