I loaded now to check and my chars were at level 5. I'll level up once-twice and try again, eventually.
She's absolutely beatable at level 5. If devil's kiss misses - you should probably just reload.
The queen shouldn't be that difficult, but I have noticed that sometimes the 3% miss chance feels like way more than that. If I ever get back to gamedev, I'm just getting rid of RNG as much as possible alltogether.
I got past the slime queen and no boss since has been a problem. I just had really bad luck that one time.
