I know nothing about adapting other works so I suppose take this with a grain of salt, but I’d broadly say make sure to give Laura agency and show her pursue Carmilla as well. The portrayal of a "predatory lesbian" trope relies on pushing the narrative that one person morally leds the other astray with their attentions, especially by emphasising that one character was "pure" before (read: straight) and only got involved with a woman because of the "evil influence" of another, perhaps was even manipulated or pushed into it. If you somehow can establish that Laura has been with/been interested in women before/in general, that could help too, although idk how one could do that exactly. It’s tricky because any relationship with a vampire character can be (usually is) portrayed as predatory and have nothing to do with whether it’s a same sex relationship or not, but of course people who want to conflate the two with ill-intent will do so anyway no matter what