Since know one wants to speak for Squigly, I guess I'll give it a shot.
As all of you probably know, Squigly has the ability to pressure/punish the opponent from just about anywhere. It takes a charge plus a bar of meter, which the bar is what you should be worried about. It is extremely easy for squigs to get a charge, and you can always set up your combo to get you one. One of the problems she has however is meter. Her meter building in combos isn't too shabby (unless you start with things like sbo, silver chord,or daisy pusher), but getting meter at neutral is very impractical unless you have no bar at all.
Characters like peacock and parasoul throw out projectiles all the time which gets them a lot of meter. Squigs however doesn't really have an option at full screen. The only thing you should do at full screen is get your dragon's breath charged. Serpant stance is really not that important to level up, and trying to zone with tremelo is pretty risky without assists to help lock the opponent down.
Her pressure can be really safe as she has stance cancels. If the opponent pushblocks, she can just stance cancel if she suspects a pbgc. You can even use stancels to bait pushblocks (ex: c.hp cancel before it hits). Obviously way better if you have a charge.
Mid screen I would say sbo is her best option. Not every character can do something about it. You can also do j.mk from this range which can cross up and like double's j.hp, it can be fast fallen for additional mixup. J.lk can be used if you suspect your opponent to jump. Even if they don't, you recover before you hit the ground allowing you to block or do your double jump
On defense, it suffers a lot if you don't have dragon's breath charged. Daisy pusher can be good against some members of the cast, but i'm sure you all know that means nothing if they have an assist they can tag into. A really good option is pushblock into sbo. This can catch a lot of characters in recovery depending on your timing. Sbo dhc'd into something can be a get out of jail free card if you have the right character for it (big band is bad, parasoul is pretty good etc).
Squigly's damage is really good. She can get decent damage output without even using a bar. With seria, she can get over 8k. Having an assist like brass H can get rid of the need to use meter or a charge to breach 7k.
Mixups and resets are very solid. Her ground resets become godlike when she has a charge. She can do so many fake outs. On top of that she gets access to center stage > daisy pusher which can be center stage to sbo if you jump as she has plenty of time to see what you do. She has a really good air vortex that works on every character. She has the option to crossunder, fake it, high/low/throw and double up with low > throw, low> high etc. Also her j.lp can fuzzy everyone, and on bella and bb it's an instant overhead.
Her movement I would say is a toned down version of val's. Squigly is really floaty, so her double jump takes her farther than others. She can attack at weird angles thanks to j.mk, j.mp, and her divekicks. Know where near as good as val though.
On teams she doesn't offer much outside of lockdown assists which in comparison to others, aren't too great. Characters like parasoul still appreciate a lockdown assist though. She also offers safe dhc's and some interesting ones if you dhc from her (like sbo > bandwagon). Also daisy pusher has a lot of invincibility, which is helpful in some situations. On point she can get the starting momentum with sbo on some characters. Some assists can make it work on those characters it didn't before. Having an assist like cerecopter, can net you some meterless pressure. As anchor, she can make great use of the meter you left her by getting out of pressure and starting her own.
Matchups ( Not having meter or having a charge changes some matchups)
Fortune, 6/4 Squigly. You win air to air and fortune can't do anything about sbo. pushblock into sbo works on her. Squigs doesn't really care about the head and again wins air to air.Without meter I still say squigly wins
Peacock, 6/4 Peacock (6/4 squigly with a charge) Hard to get in. Hard to get a charge.
Painwheel, 6/4 Squigly (not because of j.hp. more pws should punish that) Pw doesn't get in for free and zoning only gives squigs time to charge. sbo at neutral just stops pw from doing anything really.
Filia, 5/5 ( maybe 6/4 filia, 6/4 squigly with a charge) it can be hard to keep her out but meter helps a lot.
Cerebella, 5/5 (maybe 6/4 bella) Bella is hard to keep out, and hard to push off. sbo and j.lk stops her if she jumps.
Valentine, 5/5. It can be hard for either of them to open up the other. no meter doesn't hurt sguigs but meterless val gives squigs more options.
Parasoul, 6/4 Squigly ( maybe 7/3 with a charge) Parasoul's j.lp > call assist is probably the only thing squigs can't do anything about. j.lp by itself gets punished, zoning gives her time to charge. With no meter squigs has to go in. Plus Parasoul can start abusing her jump ins and blockstrings.
Double, 5/5
Big Band, 6/4 Squigly (possibly 7/3) He can punish j.hp with beat extend or a train but i think thats it. There really isn't much else he can do. I can't think of a situation where he wins. Please help BB players
Fukua, 5/5 (maybe 6/4 squigly) Dash under air fireballs or you can put up a sbo to block them for you. Not hard to get a charge. No meter hurts a little but not a lot.
Overall I think squigly is mid-tier. Just as good as Double if not slightly better. She has the ability to pressure without having to worry about reversals. You are never too far away from her (unless you are peacock). Meter is pretty important. I wouldn't say she is meter dependent, but it gives her safer/better options. Her assists aren't so great. Dhc's well with others. Has decent matchups. She's very solid.
P.S. I got tired of typing this like halfway through so if i said anything that makes no sense or just didn't fully explain, I'm sorry.