I do think she might go off of Jeju island to travel, maybe to China or somewhere else, for a wellness retreat, re-center herself and all that. But I don't think she wouldn't tell the girls or at least Rumi about it because secrecy is what drove Rumi to ask her for assisted-suicide, so if she just...left without a notice, Rumi might interpret it as confirmation that Celine didn't want her, to the point of not even wanting to be in the same country as her, and now that Rumi achieved what she wanted, and Celine finally fulfilled her role as mentor, she can finally be free of Rumi. And despite how wrong she went about it, Celine's intention was ultimately to protect Rumi from a world that would tear her apart (literally and figuratively) for being a different kind in every sense of that word, she wouldn't want Rumi to hate herself even more.
If Celine had an ounce of love for Rumi (which she makes it very clear she does), she would tell them. But it's probably going to be a somewhat formal text or letter because 1.) The girls might not want to see her which would make her flight from Jeju to Seoul all for nothing, 2.) As of where the movie ended, Rumi and Celine's relationship is left ambiguous and we don't know if they reconciled, so Celine might feel like, right now, she really doesn't have the right to talk casually to Rumi, even if Rumi is her child. She's not going to bow to Rumi now or anything (they're still essentially mother and daughter, and mothers are always above their daughters in the social hierarchy), but what right does she have to speak warmly after everything, to speak as if nothing happen, as if their relationship isn't different now?
