This thread is supposed to be a compilation of all kinds of findings and knowledges about Elena. I'll try to make it updated for a little while, but I can't promise because I have been busy. Please, contribute!
Unfortunately, Elena's throws doesn't give her much frame advantage and they also push the opponents way to far, even on corner. The following setup works nicely against characters with slow reversals, such as Law, Chun, Nina, Julia, Alisa, Ogre, meterless Elena and more.
b.throw, dash, f.jump hp (Safe from 6 frame reversals, empty jump is safe from all reversals.)
Lk Lynx Tail: (missing, come back later)
Sweep, wait a bit, f.jump mk (Safe from 5 frame reversals, a bit hard to do, you have to "cancel" the end of the animation... sometimes the visuals of this game doens't help much.)
Not only Ex Rhino Horn is the only version able to hit crouching opponents, it ends with an special hard knockdown, and it's also a true blockstring from cr.mp and puts you on frame advantage. Turns out there's even more, as KitL19 showed: it can also make some strong mixups in the corner. After the knockdown, instantly dash forward to hop to the other side, and from there you can take some actions to either stay there, or hop to the other side again with back+HK, cr.mp, and more. Very confusing, more tests shall be done.
Spinning Scythe no More:
Spinning Scythe is my personal choice for worst move in the game. It deals very little damage, it's a bit unsafe on block, it's not a blockstring from s.lk, it's not even a blockstring between both hits, and it's raw launchable on reaction during it's whole duration.
It's uses as safe tag options is also not the best. By tagging after the first hit, though Elena will get hit by everything, some alpha counters and launchers can be punished by your incoming character, but this is very matchup specific. Strike invincible reversals done by your opponent will almost aways hit both of your characters, leading to disaster.
The good news: Lynx Tail does everything you would want to do with Spinning Scythe, and more. It deals more damage, it's a true blockstring from s.lk, hits low, gives a nice hard knockdown, it's very safe (only punishable by the quickest supers in the game), it's also a very good option for safe tags (lk and mk not only tags you safely, it gives you frame advantage; Hk version will keep the opponent locked), and Ex versions gives you good options for damaging solo combos. It's only downside is that it's also raw launchable (no surprise, it's a low strike). Hk version also can be interrupted after the second hit, but that's no issue if you're planning to tag.
Hk Scratch Wheel is also a simple but effective way to tag safely.
Vanilla's Days are Over, Get in Their Faces:
SfxTk 2013 no longer rewards "lame" gameplay as it used to, so it's very important to develop an offensive plan, even if this game's focus is still perceived as footsies. Get a read over your opponents style and find your way in.
The best thing about Elena's high/low game is that your opponent can't really count on reactions alone all the time, f.mk (overhead) and df.hk (low) are too fast, and she also has slower, but safe options to mixup as well. So they have to antecipate and commit.
A quick example: after cancelling cr.mp with Mallet Smash a couple times, try cancelling into Rhino Horn. If you conditioned your opponent well enough, you'll be reward with some nice frame advantage on block.
This opens some interesting possibilities for Elena. Both Mallet Smash and Rhino Horn leaves at very good advantage on block, and it should be your goal as a Elena player to perceive when to use these moves during footsies and start your offense.
Also, Elena's dash covers a lot of distance quickly, so you can aways dash in during the recovery of some random whiff and begin your stuff.