TL;DR: It depends whether you're killing a character or perpetuating a stereotype.
What's the trope?
What defines the "bury your gays" trope is first and foremost a character whose defining characteristic is "gay". They're token characters, thrown by the wayside with little fore- or afterthought.
At the heart of the issue is that it's a way to tick boxes and give the illusion of inclusiveness, without having to bother with actual representation. And then it also has the unfortunate implication that these lives have little to no value.
How do avoid playing straight into the trope?
You can start by making the character an actual character, not defined by their gayness but by their wants, needs, hopes, dreams, experiences, and so forth.
Having other well-rounded characters from the whole LGBT rainbow would also be helpful to mark the difference between killing the gay character and killing a character (who happens to be gay).
Is it okay to kill of a gay love interest?
It's about as okay as killing any other love interest.
As far as the myth of Orpheus, Eurydice just exists to give some motivation to the hero. Killing the wife to send the hero on a righteous rampage is a story that's been done. The thing you have to acknowledge here is whether it's a dead wife, a taken daughter or dead puppy dog, none of these are characters, they're plot devices.
The way I see it, you're more likely to run into women in refrigerators (see also Stuffed into the Fridge) and damsels-in-distress territory. The revenge action genre has long faced criticism for using women to give the man a motivation for cheap, and that never stopped any of them from being commercial and critical successes.
You could leave it at that if you're only interested in the revenge part of the story, and having a lesbian hero avenge and save her lesbian lover would probably do more to subvert these tropes than most others.
If you're not satisfied with your love interest being a mere plot device, it's worth considering two ways to explore that character's hopes and dreams and wants and needs, and such.
First, whatever relationship exists between the hero and their loved one, it has to be shown, not told. Don't just label them as girlfriends, show us that they care about each other, or at least why the hero cares.
Second, make the character live beyond the grave. By that I mean have their presence felt throughout the story, e.g. through memories, objects they left in the hero's home, other people that knew and cared about them, etc. People don't just disappear from Earth when they die, what they leave behind is a great way to explore who they were.
The resurrection angle also opens the door to have them observe the quest of the hero from the great beyond, or even narrate the whole story from their ghostly point of view.