@daallday as long as she's still alive and have some degree of freedom, she can build up another network/connection/resource in secret so her brother paranoia is understandable, because her brother knows very well how she can lie without batting an eye and have been scheming for her whole life. Heck, even the ML wanted to use her talent to dethrone her brother on the original timeline, before her accidentally being sent back to the past alone.
@mldyx It's not like anything would automatically be added in his favor because she wasn't there, really. They wouldn't have much to say about him in his favor for being the child of the Emperor and a mistress, they just wouldn't have anything bad to say about him for having a half sister of questionable origins. The absence of a demerit isn't necessarily a merit, but it's still better to have as few demerits as possible, ordinarily.
As for whether she was born deliberately, probably yes. But that would've been to create an heir to the marquess. The mom kind of went ahead and murdered the other people fitting that bill, so the daughter she worked so hard to make was just for securing a position in that household. Ultimately that all worked out just fine for him, with his sister's help behind the scenes as a member of that family in the first timeline being what actually put him on the throne, but he doesn't know that here.
@Glomoro i'm actually confuse on these bits in your reply
"Her even existing at all looks bad. Nobody will say anything directly to Lawrence because of it,"
"they just wouldn't have anything bad to say about him for having a half sister of questionable origins." are you saying that Tia gets all the insults here because of Lawrence? compared to him anyway.
@Kingdo
It's basically the same thing with Hourglass.
In the first timeline, the bad guys are depicted with having 9000 IQ.
But when we get to know them in the second timeline, they have like 10-20 IQ.