
Babe, it isn’t grooming. Grooming is intentional. It involves abusive behaviors like isolating the victim from other people and stepping them progressively through behaviors they’re not comfortable with. The fact that he’s considering who her natural partner will be in the future and honoring her autonomy are the exact opposite of grooming. Please look up the actual clinical definition of, the internet has twisted it three ways to Sunday.

No this is grooming even if they are kind to her, they are all repeating all the time that she is his fated mate and he will suffer without her.
She also don't have anyone else to rely on. They saved her and her friend from a gruesome (short) life and she is a kid. Obviously she will latch on them. Even if they are not abusing her they are still pushing her in one direction (marrying this old dragon because she is his mate and he can't live without her)

I love how you’re applying “even if they’re not abusing her” to a term that is by definition abuse. Reeks of “I don’t care if Belle asserted herself, it’s Stockholm Syndrome because I say it is.”
Definitions exist for a reason. It may not be the most kosher situation, but that doesn’t make it grooming.

They are not abusing her outwardly but promising her to a old man is grooming.
Sexual grooming is the action or behavior used to establish an emotional connection with a vulnerable person – generally a minor under the age of consent[1][2] – and sometimes the victim's family,[3] to lower their inhibitions with the objective of sexual abuse.[4][5] It can occur in various settings, including online, in person, and through other means of communication.[6] Children who are groomed may experience mental health issues, including "anxiety, depression, post-traumatic stress, and suicidal thoughts".[5] - Wikipedia. And other websites have similar definitions

They’re not promising sex, they’re promising love. Those are indeed two different things. It was his friend who first acknowledged that the relationship wasn’t always a romantic one, but could also include various forms of platonic relationships. I take their “establishing an emotional connection” more as affirming for an abused child that they are in a safe and loving environment, and that holding back won’t produce anything good.
Also, Wikipedia is not a reliable source and has skipped a few steps in their opening definition. Secrecy, threats, lies, and division tactics would be basic reasons for the mental health decline, and again, those aren’t present.
Also-also, I wouldn’t trust artlapsa translations enough to make any real arguments about word usage. They’re barely passable on the best days.
In the end, if you’re squicked, don’t read it. But this one still doesn’t read like grooming.
Seeing him mention her finding her natural partner made me breathe a sigh of relief lol. Like sure, they’re obviously going to end up together and this is 100% still grooming but it just makes me happy that HE isn’t thinking of her like that. He just loves her, not romantically, but platonically. We of course know that’ll change but thank god he ain’t thinking of romance with a child lmao