Gonna favor Cong here. While I'm not entirely sold on her just yet and I do think the UFC is trying to push her as "The Alex Pereira of WFLW", I do think she has some modicum of talent and more importantly Fernandes has done nothing whatsoever to impress me.
Gaby got badly dominated by Jasmine and Tereza in her first two bouts. Then in her last fight she barely managed to eek out a Split Decision against Carli Judice... the very same 3-1 Carli Judice who got handed a pity contract despite losing her appearance on Contender Series, mind you. And honestly there's a good argument for Fernandes losing that fight! I'm not sure what Fernandes does particularly well. She seems like a very dime-a-dozen Brazilian fighter. She has decent timing on the feet and isn't afraid of a bit of a scrap, but she is no great striker. A bit plodding, in all honesty. She's physically strong I guess, but nothing special. Her takedown entries are very basic and she doesn't have much of a top game. If she tries to stand with Wang Cong for any period of time, I think she's going to get beaten up and lose a one-sided Decision, maybe even TKO'd.
If Fernandes chooses to grapple -- which I imagine she will given Cong's pedigree and the fact that Wang is still untested in that area -- I think Gaby's chances improve but not by a ton. She is the one with the history of getting badly outgrappled (just look at her first two UFC fights) and even against Judice she struggled to take her down and hold her down for much of the bout, with Carli scoring some TDs of her own no less. Cong comes from a Sanda background, which unlike most kickboxing styles actually incorporates Judo & wrestling style takedowns into its curriculum and ruleset even if it doesn't include subsequent groundfighting. She also has just as many subs as Fernandes does on her record (two), albeit against questionable levels of competition.
The thing is, when Fernandes chose to grapple against Judice it clearly gassed her out very quickly and very badly. Even if she's able to take Cong down and win a round or two with control time, I suspect she'll look dead in the water by the time Round 3 rolls around... which is a dangerous prospect when you're standing in front of someone like Cong.