Can anyone give me some pointers on how to deal with Sindel? Her (I think) b1 hair whip normal is blowing me tf up. I can kinda whiff punish it, but it's a bit hard.
Her F1 is the move your talking about, you can low profile the first hit being a high.
On how to punish it really depends on what character you are. You can backdash into specials on wiff, or force your way in and enforce pressure. Her B2 is her jumping mid used to go into flight cancels and all the pressure is semi fake if you hold up and block while looking out for her to cancel without doing jump in Punch which beats your armor.
Her neutral is her D3, B4 and F1 and close up is her 11(-4 on block starter), 24(9f high starter that's +2 ob), B2(14f mid).
If your character doesn't have decent range then you either have to learn wave dashing FFxxR2xxFFxxR2xxF into whatever strings you would use for decent range but also fast enough to punish or you will have to use Special moves after forced wiff by your backdash.
Sub Zero has Slide or Clone Push.
Mileena has Roll, teleport or Said.
Reptile has Slide, S3, 24(on read) also instant air sky dive.
Kung Lao has Shaolin Shimmy and dive kick.
Some characters literally don't have anything fast enough like Rain. But his solution is keeping her fullscreen or getting one knockdown wave dash to OKI and keep momentum in her face with constant mix on wakeup.
All characters have Kameos to help and all characters have Kung Lao Low Hat which is essentially a get in risk free card. To hold it and approach with mix, HTBs work or simply throwing out powerful unsafe moves that are made safe with low hat hitting just after making it +2 on block and really+ on hit with combo follow up.
Have you tried your characters B4?
It would really help if I knew your character you're struggling against Sindel's F1. I could go lab up the answer for you.