The Kardashians are business oriented and they are not playing with one of their assets–their family name.
According to a TMZ report, “Kim, Khloe and Kourtney Kardashian are sticking to their guns when it comes to stopping Blac Chyna from the family name — and neither marriage nor their mom will change that.”
The website adds that:

Sources close to the sisters tell us they will not withdraw their opposition to Chyna’s application to trademark “Angela Renee Kardashian” — despite Chyna’s side saying there’s no legal war brewing.
As we told you, BC sources say Kris Jenner reached out and promised to call off the lawyers. But our K sis sources say that’s not how they feel about it. We’re told it’s nothing personal against BC, just biz — they feel adding an extra woman to the roster will dilute the brand they’ve worked so hard to build.
We’re told they think it’s odd Chyna didn’t move for a trademark when she was with Tyga — although that’s kinda apples and oranges. $1 if you know his last name.