This is a big trap many players fall into. Question did you go into the guard room/mess hall and read the tutorials? If not, you WILL have a hard time, the reason behind this is how she lvls up. You CAN do a straight combat build without ever using sexual skills to beat the bosses in the game, I have done it on my first playthrough, 2nd and now 3rd. It's a matter of your build, while yes, a slut build is OP but so is an actual combat build when you spec right.
For example, EVERY attack is scaled of strength so you NEED to spec into strength regardless of your preference, so what about your second stat spec? Agility is your best friend in the whole world if you do ANY combat runs that should be your 2nd growth stat. Now your 3rd, this is where it gets tricky cause you need dexterity because it affects crit and Accuracy to hit an enemy, but what about energy and will power? Your 3rd spec is to find a mix within those 3, cause dexterity IS important but not super important for a combat build; personally, I went for a combo of all 3 for my last spec. But none of those skill growths topping strength, a lot of ppl don't read what's in the guard room/mess hall because they want to get to the content faster which is understandable, but you miss out on understanding the game because its slightly more complex than it leads on.
TLDR; Combat= Strn + Agility + (whatever 3rd spec you want) and make use of TAUNT during battle. Confident buff is OP and if you can get the diamond necklace that allows for a chance to start a battle with the effect, get it. Also, mix and match accessories, it explained why in the guard's room.