You have the perfect in. I mean really, she has a splint on her sucking thumb hand and she went to sleep without sucking it.
Praise her like crazy, tell her how grown up she is, go out and buy her a small gift to show her how proud you are of her, that she is a big girl now and can sleep without the finger and now her teeth won't be pushed out and make her talk funny. Trust me it happens, my brother couldn't be stopped sucking his thumb and his teeth got pushed out and are in terrible shape to this day.
How long will she be in the splint because time is of the essence. Stay on the praising stuff let her call her grandmother. grandfather, aunts, uncles, anyone, really make a big deal with it.
And for all you moms out there that have kids that suck thumbs or binkys, this worked for me. Mine sucked their thumbs, and when they started doing that at 3 months or so, I gave them a special blanket made just for them. They only got the blanket at nap time, they couldn't carry it around with them places or play with it, it was only special for sleep time. When they were 18 months and old enough to understand we told them they were big boys now and the blanket had to go in the place of honor, the cedar chest. Well, since they associated the thumb with the blanket they quit sucking their thumbs. They would visit their blankets at times but never asked for it to help them sleep. It worked with all three of mine and two nieces, so give it a try if you worry your child will continue to suck the thumb or binky after 2, (and really that should be the time), these kids at 6 and older in carts riding around with binkys in their mouths really look silly, sorry I call it as I see it.
Good luck with all that.