There aren't canon lesbian moments between them, but in the 90s anime, there were plenty of subtexts. Ami blushes for Makoto a LOT of times. And Jupiter's infamous stare at Mercury's butt when she tripped. And the dance scene. And the fact that they are often paired together. And they have a canon song when they have a sleepover, just the two of them, holding hands and talking about their feelings and fears.
So, no, they are not a canon couple. But I've seen ship sailing with not even half of what they have. They are basically Haruka/Michiru in training.