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So like Lila makes everyone turn on Marinette including her parents (sorry Tom and Sabine) except Alix, Luka and Kagami. Unfortunately, Kagami's mother decided Paris was too chaotic and they moved back to Japan while Luka went on a tour around the world with his dad Jagged Stone. Both of them still tried to keep in contact with Mari and the others but because they could only talk over electronics they weren't able to help Mari until way later. So with only Alix being able to help actually she wasn't enough and Mari slowly cut herself off from others in a state of depression the only reason she was living was that she didn't want to burden Alix with being the guardian alone (she made her a guardian but Mari was the grand guardian so she had more responsibilities.)
When they turned 25 Kagami and Luka came back and at the four of them finally beat hawkmoth and travelled to the temple so they could protect the miraculous and Kwamis (when the temple was restored after feast all the objects came back but when the guardians came back they rapidly aged so Marinette now had a secret magically fortified temple filled with a bunch of mini gods with only her and her three friends to restore it) at 30 Alix decided enough was enough and that Marinette gave up enough for the world and she deserved to be happy so Alix decided she will go back in time and save Marinette from being depressed and lonely.
She told the Kwamis what she wanted to do and they agreed so they went into the burrow with the Kwamis (only a few so that Marinette wouldn't get too suspicious) and looked at all the possible timelines and made various plans until they decided on one. Alix went back in time to when they were 17 and with Trixx she made herself look like a regular woman in her late twenties and sought out Ladybug and introduced herself as a descendant of a guardian that also escaped the temple being ruined and that she was currently living at the recently restored temple (in this Mari got the miraculous at 15 and became the guardian at around 16 and a half) and was taking care of the Kwamis there and offers to help her with the hawkmoth problem. Mari tentatively agrees and they are asked to help her defeat hawkmoth.
When they win, older Alix teleports them with Kaalki to the temple and teaches them everything that they learned themselves and tells her about the imbalances in the world and the lost Miraculous scattered around the world. At 24 Mari leaves the others to go about their lives and guard the temple while she travels. On her travels she destroys the pits and steals/saves Jason, Damian and a clone that she found(Heretic) that were there because they hadn't left yet. So she heals Jason of the pit madness and now she has three kids, a 17 year old and a pair of 7 year old twins. They travel, she maybe adopts others like Conner and they eventually get to gotham where she meets bruce and they either raise the kids together as friends or as a couple whichever you want.