Nothing in the book says Gambit was aware of the invitation. That is an assumption being made by you to justify your narrative. All that is in the comics is the fact it is clear Bella was not invited and Magneto was. If the writer wanted us to believe Gambit agreed to Mags getting an invite then it would have been simple for it to be said. It was not.
If we are going to just blindly speculate then it is just as likely that Magneto waited for her to be alone before he approached her. That is no less speculation than you claiming Gambit knew about the invite.
Well going but that logic of yours, Nothing in the book says that he wasn't aware either, s*** happens off panel, when the x-men arrived did we assume that they were not invited or asked to come because there was no mention of their own invitation, no, because we as readers we know the invites were made off panel, Magneto says he was asked there by Rogue . Just because it was not stated on panel doesn't mean that Remy didn't know or he may not of known but it would have been all kinds of awkward if Mags had shown up without Remy knowing.
There is no speculation about the pairs meeting, its fact of how it happened in the book, she was down and spent after the fight, look at how she is drawn in that scene, that is not the depiction of someone sneaking around, hell all Gambit or any of the X-Men would have to to is look up and they would have seen them, its not the actions of two people sneaking around. Also Magneto wonders if she lured him there as in to fight/trap him for being on the dark side again, again not the actions of two people sneaking around,
if your sneaking around with an ex you dont do it out in the open and you dont invite him to your new home where your husband and you are throwing a party , you dont invite them anywhere near that
.As i keep saying im not a fan of Rogue, Romy or the marriage i want him far away from her and it would suit my narrative if she was sneaking around id be on your bandwagon, id want the marriage over (kinda already do) , we are not the only fans invested in this and there are Rogue and Magneto fans or just Rogue fans who wanted that meeting to happen, the conversation was total BS, like Magneto the dude who put Gambit on trial is suddenly all knowing when it comes to his feelings, that's worth getting annoyed over, there is plenty wrong with this book, and plenty of evidence that this marriage is doomed, but Rogue did not sneak around