I'm talking about characters like Kokoro, Christie, Helena... characters which just seem to have an endless ability to keep pushing forward and attacking. Other than 2p and 4h+k I'm really struggling lately against these rushdowners. Admittedly I'm talking about online, so that probably doesn't help. Is it just a case of learning how and when to counter the opponent or are there any good interrupt moves I'm totally missing? I have no fucking idea what Kokoro and Helena are doing so just tend to eat up the pressure. Grateful for any advice from expert Lisa-ers, thanks.
You're going to need to be patient in all of those matchups, Lisa does not have many good crushes beyond the ones you've mentioned, though don't forget about BT 4P as it can be useful in certain situations, and 1P which is slow but solid. 4H+K is a great move, but you can't rely on it due to it's unsafely and 2p is often a risky bet as at 16 frames it's slower than most mids.
Also don't forget that unlike most characters, Lisa gets unblockable followups if her jab lands on counter hit and is + on block, so don't be afraid to throw it out there when you know it's your turn.
Depending on the player she can be very difficult to get away from as she has many safe moves such as 66P and her 6ppp string that you cannot throw punish. Look for opportunities to throw punish moves such as 6KP and 3k4K that many Kokoro players are used to getting away with that you can punish due to Lisa's faster throw speed.
Kokoro has a lot of strings, but the general rule is that she doesn't have any tracking outside a few specific moves so if your opponent is finishing strings be sure to sidestep as Lisa's sidestep P is fast enough to be guaranteed in a lot of those situations.
If they aren't finishing strings you're going to have to make a read on free cancels. I'd recommend using mids as Kokoro has several solid high crushes that a competent player won't be afraid to use. Don't be afraid to sit and block, as Kokoro does not have any stunning low options to open you up. You can afford to be patient and wait your turn unless they start going for Heichu throw which will force you to start hitting buttons.
Helena is not much faster than Lisa, but she has incredible crushing moves and bokuho grants her a lot of evasiveness. Study Helena's strings and learn when you can throw her, Lisa's low offensive hold is very useful in this matchup.
Be careful going for non guaranteed throws and OHs in the neutral because Bokuho will stuff that along with highs. Be wary of going for mids that she can Bokuho duck (4H+K can't be ducked).
Like Kokoro Helena doesn't have a lot of tracking, but unlike Kokoro she has lots of stunning lows that you need to watch out for. There really isn't much else to say beyond be patient, block and punish and try to get her off of you ASAP. She's also not that safe unless she finishes certain strings, many of which only have one possible followup.
This matchup is incredibly abusive, Christie has an 11 frame mid you can't even bank on 4H+k at round start. She's much faster than you, and has many strong tools that can prevent you from getting an offense started.
Christie has incredibly long dynamic strings, many of which can transition into her JAK sidestep stance. Luckily as Lisa you can low OH her out of some of those situations. You're going to need to just study her strings, there really isn't an easy way out of that as she has tracking in weird places, safety where you'd assume there was frame disadvantage (hit 9P on the training dummy and try not to be upset) and other things that won't make sense without looking at it in the lab first.
If there's any saving grace in this matchup it's that Christie's throw and hold damage is pretty low (do be very sure to keep your back against the wall though) so you can afford to be a bit more forceful with your holds and strikes. For all her pressure, Christie does not have many stunning lows (though many of her lows have followups), so be patient and stay focused on catching her free cancels and finished strings.
If you ever encounter these characters again, be sure to save the replay. Even if you don't post it you can ask for help with specific moves that were giving you trouble.