I'm a bit surprised by Chelsea transfer strategy, they seem to want to sign every talented young player. Hansi Flick has said he will try to keep Fermin Lopez, but he hasn't ruled out the possibility that Barcelona might sell him if they receive an attractive offer. Barcelona financial situation isn't fully stable yet, and Chelsea might be looking to take advantage of that, thinking Barcelona would let Fermin Lopez go for a low price. With the transfer window closing soon, Newcastle is also reportedly joining the race to sign Fermin Lopez.
Flick wouldn't allow that to happen. If it was only Barcelona management, Fermin would have been sold. He is very important to the team and based on what you said that Chelsea wants him at a low fee in order to take advantage of Barcelona unstable finance makes it impossible. No club will sell a player that is very active in contributing to the the performance of the club lower than his value.