I'm not convinced that stealth will be too useful here, when her opponent passively has all 5 of her senses very sharp.
Combat skill helps Webby. You might argue Webby has more experience, but Winter is far from unskilled, as she did quite well in a 1 vs 4 scenario and even killed one of them.
She combines her cqc with her wall magic to control the flow of battle, corner or trap her opponents, and can use her walls for both defense and offense at the same time. A wall could block an attack, a second wall could come from below Webby, while a third and fourth come from other directions to crush her.
The location of the fight helps Winter actually. Since her walls need to be created from an existing material around her, the fact that there are so many houses will benefit Winter, as she can use house walls, stairs, or city ornaments to create walls from, in addition to doing so from the ground.
Finally, if Winter gets to grab or take hold of Webby, Webby wouldn't be able to escape easily, given the massive LS gap. Then, Winter could smash Webby against her walls, which she has done in-chatacter.
