"I dont know how to avoid S.Lab's BI,and don't tell me all the ways to avoid it because I'm not gonna do it."
in terms of best situation, definitely block it. if you are fullscreen block it, hell if you are fullscreen run up to her and block it just incase. If she's doing A version BI which is pretty damn fast you block it or roll it, you can't jump post flash because it'll catch you in the air, and jumping behind is also risky as it covers over her head.