Even with only one season of The Witcher released on Netflix, it's clear to everyone that Geralt and Yennefer have a very complicated relationship. They may be very attracted to one another, but that doesn't mean they're friends. In fact, it actually works against a real friendship.
They are not particularly good for one another, or very supportive. It's complicated is an understatement, and its time to explore Geralt and Yennefer's relationship for what it is, and that's not a friendship. Friends help one another and, at least in the first season of the show, Geralt and Yennefer don't offer that to each other.
Used Geralt
Yennefer may be all smiles when she meets Geralt at an orgy and he asks her to help heal Jaskier. Yennefer, of course, only agrees to assist Geralt because she wants to harness the power of the djinn that he has with him because it injured Jaskier. In this instance, she's only useing Geralt, and that's not a mark of friendship. It's also not a healthy start to a positive relationship, even if they just met. Yet, they continue to pop into one another's lives. It seems that Yennefer only shows up when she can get something from Geralt.
Paralyzes Geralt
In the novels, when Geralt and Yennefer both join teams to go after the dragon, Yennefer paralyzes Geralt for a time so he can't stop her from going after the golden dragon. That's not really what friends do, even when they disagree. They don't talk it out, Yennefer just goes after Geralt and then goes off on her own. It's not what any healthy relationship looks like, particularly a friendship, and there's a lot more where Yennefer uses her powers to then use Geralt.
Uses Geralt to Attack Villagers
When Geralt comes to ask for help healing Jaskier after he was attacked by the djinn, Yennefer does not only agree so she can attempt to take on the power of the djinn, but she also agrees to use Geralt's talents for her own gain. Using her magic, she is able to get a mind-wiped Geralt to attack the villagers who did her wrong before he even arrived. That's not a great look at the start of a relationship that many believe grows to be a positive friendship. They're not really friends in the end.
Doesn't Help Get Geralt Out of Prison
Yennefer doesn't just use her magic to have Geralt attack the villagers who did her wrong when Geralt is arrested for his actions, she doesn't come to help get him out of jail.
Not that Yennefer should have used Geralt to attack the villagers in the first place, but the fact that she then doesn't help him get back up and on his way proves that her thoughts are always on number one, herself. It's hard to have a real friendship with anyone when a character is as completely selfish as Yennefer seems to be.
Kiss and Flee
Geralt and Yennefer are great fighting partners when they decide to protect the dragon they were once hunting in the first season's "Rare Species" episode. Yennefer and Geralt even share a rather passionate kiss while they tare apart everyone around them to keep the dragon alive. However, once their services are no longer needed, Yennefer heads off with hardly a second thought. It's not very friendly to lead Geralt on and then move for the exit as soon as the opportunity presents itself.
Geralt Loses The Djinn
Geralt, in the end, is responsible for the escape of the djinn, since he was the one with the three wishes, to begin with. He is aware that Yennefer's greatest wish is to keep the djinn, but he lets it go anyway. Of course, Geralt knows what the djinn is and what it's capable of, so letting it go seems like the wisest choice. But, it's not the kindest. He's less than supportive of Yennefer here, very unlike a real friend would be.
Geralt Doesn't Listen
Geralt keeps going after Yennefer. It's clear he is smitten. Yennefer is a bit more complicated. As with the dragon incident, Yennefer seems to clearly let Geralt know she's not interested in hanging around and building a romantic relationship—or a relationship of any kind, really. If Geralt was really Yennefer's friend, then he would respect her choices and pay attention to the signs she is offering him. Yet, he keeps coming back and being surprised when she walks away.
Romance Leads to Friendship Problems
Geralt and Yennefer's relationship has always been more romantic and problematic than friendly. Their continued attraction to one another makes it complicated to build a friendly relationship of its own.
Romance can make being "just friends" its own issue. The pair could never be real friends because their attraction to one another makes their interactions volatile and keeps them from discussing other important aspects of who they are and who they want to be.
Jaskier and Yennefer Don't Get Along
Despite his protests, Geralt has a best friend, his name is Jaskier. Unfortunately, Jaskier and Yennefer don't exactly get along. Jaskier doesn't like what Yennefer does to Geralt, and Yennefer does not appreciate Jaskier's particular sense of humor. This makes Geralt being friends with both Jaskier and Yennefer slightly problematic. And, since Jaskier was there first, Yennefer was going to have a problem making friendship work with Geralt.
Geralt Doesn't Know Yennefer
As seen in the first season of The Witcher, Yennefer has a very complicated back story that she doesn't share with Geralt. She used to look very different, she comes from a farming family, and her training at Aretuza was a little bit abusive. To be real friends, Geralt and Yennefer would have to be open with one another. Yennefer certainly isn't great about being honest, and that kills a friendship before it even has a chance to get off the ground.