I wouldn't be too fast discounting her as "no threat". She's survived late into the finale for a reason, and she's pretty much in a similar position as Galina in KOD (who nearly killed a main character, and an fairly high profile secondary one, Morgase)

She can't channel (unless Moghedien pays a visit on Moridin's orders and Liandrin gets "reactivated", shown how to disguise her ability and how to invert... lured to think she might redeem herself though in truth expected to carry out a kamikaze/suicide bomber style of mission), but she committed her last murder as late as KOD, and it was revealed she has access to poison (she killed the last woman beside Suroth in Seanchan entourage who could explain how Suroth is tied to sul'dam. Alhwyn probably had a lot more leverage on Suroth than this in truth. etc.). Suroth had started to think she had become too much of a liability, but she was arrested not a whole lot of time after that, and it sounds likely she had not yet taken action about her (it was delicate, Suroth was weighting the pros and cons of having her leashed now, after waiting so long. Why she was made da'covale isn't so extraordinary... she was useless as damane, and safe to keep unleashed, but was still AS and couldn't be let free, and deciding to have her leashed now could raise questions).

It's unknown what happened to Suroth's human properties after she was made da'covale herself, but it sounds unlikely Jordan kept Liandrin until so late in the finale without a purpose, and reminded us she was still dangerous in KOD. AS prisoners could recognize her, but damane, especially those in training, don't spend a lot of time with the household da'covale (barely any at all, baring the occasional outings or when damane are used as bodyguards).

It's a distinct possibility Suroth's slaves were forfeited to Tuon (in her mother's name, at the time). Liandrin is known well by both Moridin and Moghedien, and it's probable they know or can find out where she is.

It sounds like a distinct possibility Liandrin is still a threat, and will be ordered by a Forsaken to kill the Empress to throw the Seanchan in chaos now that the Shadow has lost Semirhage to "orient" her in the desired direction (though so far, Tuon has done a good job doing what the Shadow might hope for). It would be very ironic if Tuon decides training the captured Amyrlin Seat will be her new pet project (I somewhat expect that, or at least that Fortuona will take a personal interest in her training.. perhaps charging Melitene to train her if as Empress she's given up the hobby of training damane herself), and Pura ends up saving the Empress's life by revealing one of her da'covale is BA (Liandrin being one of the only sisters Elaida is convinced is Black...). One reason I think Jordan was planning to bring Pura into Tuon's entourage is the fact the woman who betrayed Elaida and put her in much trouble (Dumai's Wells etc.) may also be around (that'd be Sevanna, of course, and Elaida knows about Sevanna and the Shaido).

It's a nice nest of villains of the criminal type that are massing in Fortuona's entourage for the finale, facing Seanchan justice as slaves, and we may not have seen the end of it just yet. From what Perrin said about the Shaido in in TGS, and with the fact the rakens are back patrolling in the east en masse and central east Altara is crawling with Seanchan soldiers, the lesser known pass into the mountains has collapsed after the Band (convenient), leaving only the main pass where the Seanchan were looking for Mat and watching over Murandy, then the fact Roedran has mobilized Murandy and likely looking south-west for a probable invasion, and finally Rand's forces are massed on the Altara/Illian border, and toward FM are the huge forces of the Bordermen, and in Andor are Elayne's. I wouldn't bet too much too soon we've seen the last of Therava and Galina. It sounded likely we had in KOD, but after TGS not so much, and the Shaido are really quite trapped in Altara. We could even get a Liandrin/Elaida/Galina reunion in the damane kennels before TG (ironic if so that Elaida trusts Galina blindly yet has said straight out she was sure Liandrin was a DF and BA... Liandrin on the other hand possibly knows Galina is BA), Jordan may not have planned to use all these possibilities, but somewhere in there must be something that will indeed happen.