um was she trying to help crash the wave?
this happens to me all the time when i play sup, i try and help a lane or something then the ppl leave so ofc we need to crash the wave asap so the ppl who left will miss that wave well not everyone understands how wave management works so ppl are like "OMg why are you taking farm" and it's like dood you need to chill, we need to push the wave in so it'll crash to tower and if you are playing Ezreal it's pretty tough to do that early on with your kit while lux has a easier time with her passive and her abilities.
Now if you started flaming the lux because you didn't understand then i would say this is actually both of your faults. If lux decided to troll you after you flamed then i could see that (i don't do that stuff but i seen ppl do it) but it all would fall on your shoulders to begin with for flaming someone for making the right play when you didn't understand the play.
Also if you were trying to back, generally speaking we try and push the wave in.
Dunno if that's what happened or not, but generally speaking when we talk about things like this it generally happens when someone got pissed, said some things and then the other person on the receiving end of the comments just is like "Oh you thinking I'm trolling you? No I'm not but NOW I will because of the toxicity you've shown to me"
if that scenario or something similar is something that happened then i would highly recommend looking up wave / lane management control on youtube or just youtube 'when to crash waves lol' something along those lines.