SCP-029
Most of 029's abilities won't come into play. Self-Sustenance is irrelevant in such a short fight, her Mind Manipulation only works on men, her ESP seems unlikely to come into play, and her Weapon Mastery isn't of much use since she doesn't have any weapons under SBA.
Her speed is equalised away, and her durability isn't anything that would concretely stop her from being stabbed by a utility knife. Her weakness won't come into play due to SBA making it night for her.
Really, her only advantage is being able to strangle grown adults, and being firmly against bloodshedding.
Risuka Mizukura
Risuka's abilities will be able to do a tiny bit but not much. She has teleportation, which could help her get the jump on 029 given the hundreds of meters of starting distance granted by SBA, but she can't spam it, nor can she use it to get out of grapples. She has healing, but it only works on wounds that would heal naturally, and again requires her to shed blood; it won't be much help if she's being strangled to death. She has good countermagic, but 029 doesn't have any magic. Magic Sigils would take far too long to create to be viable in a battle. And her resurrection/transformation requires her to die from blood loss.
Her stats are pretty garbage, she has a utility knife, so she could get some stabs in, but overall she's just a normal 10-year-old girl physically.
Their Wincons
While she could technically win by stabbing enough to kill and teleporting away, Risuka has a far better shot when dying from bloodloss, but with her opponent unlikely to do that, she'd have to inflict a large enough wound on herself. She has done this canonically; against an opponent that tried to paralyze her and starve her to death, she bit off her own tongue, creating an abnormal amount of blood loss, and soon killing her. Still, she was very hesitant to do that, only going for it once her other plans failed. On top of that, bleeding out from merely biting her tongue took a decent amount of time.
SCP-029 could win merely by strangling Risuka to death, something she's pretty experienced with. If she can strangle adults, why wouldn't she be able to strangle a 10-year-old?
From these two, I think SCP-029's victory is more likely. Even if Risuka tries to teleport in and stab 029 (when she's more often seen just running in), it would have to be one hell of a lucky stab to kill 029 before she can strangle Risuka to death. 029's larger stature might also help in that regard; it'd be pretty hard for Risuka to slice 029's neck open. If Risuka tries biting her tongue off at that time, I'd still expect strangulation to kill her before blood loss does (especially considering how she had to psyche herself up to bite her tongue off when we saw her do it canonically).
tl;dr Risuka has some outs, but SCP-029 likely wins.
