Like I said, I don't really want to overdo it with overanalyzing the kisses as not to ruin it for everybody. I will say that imo they are kinda overdoing it with "lesbian = sweet fluttery lady kisses". But of course VL are kinda used to high standards there since Claudia Hiersche was *very* good at kissing/selling the kissing and Miribecca were really unexpectedly good.
I did thought the dream kisses from the Bianca arcs gave me a hilarious "enthusiasic slobbering dog" vibe from Marlene
I'm quite curious how this will develop because *hides* to be honest, I never thought Marlene had all that much chemistry with her partners in her romance scenes taken from the sampling of 2 Hagens and Tristan (and I guess Alexander before he was revealed to be a the rapist). I thought that there was always something slightly awkward about her and both Hagen 2 and Tristan and her and Hagen 1 were kinda generic good looking but also no chemistry really. Though I would say the Marlene love scene I liked best so far is, unpopular opinion, probably Marlene and Hagen 2 at the lake. I mean it wasn't great, but it was a pretty scene, but really more for the environment, the mood, Marlene in really normal clothes etc. (and it really wasn't much of a love scene, more the stuff around it) I also don't see her as being like Jasmin where you imo could just see immediately that she was a lot more at ease/happier acting with Romina. I always thought Jasmin probably enjoyed being on the same height as her love interests and getting to be on equal terms/even getting to be the aggressor sometimes so I really bought her being into the storyline.
Tatjana we haven't really seen enough of with other partners to really say what her standard is. I thought Bianca kinda has the "lesbian = ubersoft kisses" thing going on as well. And with Ricardo you couldn't really see much of the actual kissing, it's more noticable that Rebecca was very direct and forceful in her body language (like very smoothly taking off his shirt/going for his belt).
Though I think it often shows that you can't reduce chemistry to even that. For example, with Daniel and Helena, you could see them putting in a lot of effort into creative touches/body position and it is generally agreed on that the actors are most likely dating in private life (so no problems on the kissing front). But to me they still never had much chemistry, no "leaping off the screen" type. It's funny, I never liked Helena with Andi, but I thought she had more chemistry with Andi in like their little playful boxing scene after Helena broke up with Daniel than she ever had with Daniel and again it is known that the actress isn't a fan of Helena/Andi at all and always championed Helena/Daniel. So you can't reduce it to personal sympathy/friendship between actors either or whether the actor likes the storyline or how non-stiff the body language is. In the end there are some factors that seem to be more frequent than others in successfull chemistry but when all is said and done, it still remains something unexplainable.
That said, I do get the vibe that Melanie is very "on" in this storyline, she seems a lot more animated and varied in her facial expressions than she is in her typical stories. So imo you can feel the effort/engagement. (with Tatjana you can't say much because you don't really have a baseline for what she is capable of, she seems to be doing very solid work to me though)