You didn't say she's been spayed, yet! She could be hormonally aggressive, and spaying will help control that. She may be coming into heat, and you & the boyfriend are her "targets". If she has NOT been spayed, this would be a GREAT TIME to get it done!!!
It also sounds like she may not be getting enough "interactive" attention.......meaning, tossing a toy for her to chase after, swishing a fly swatter back & forth on the floor for her to chase, rolling a ball for her to chase.....etc. Also, if you'll get some heavy ( athletic ) socks and tie them into knots, you can keep them nearby, and play "tug of war" with the socks....then, when she's REALLY "into it", toss one across the floor. She SHOULD chase after it ( like prey ), then maybe carry it around. She MAY even bring it back for you to toss again.
When mama cats discipline their kittens, they'll HISS at them! If you'll try that, along with a spray bottle of water ( mixed with some white vinegar, if plain water doesn't work with her ), that should protect your arms & legs.
If you've ever watched kittens playing together, they play ROUGH....and since she doesn't have another cat/kitten to play with........you & the bf are "IT"......If you have the space, and can afford the extra bills for vet care, you might consider getting her a "friend" ( a neutered male that's around her age ) that she can transfer her attention to........
A young kitten would be too easily hurt if she didn't "take" to it, and another female is never a good idea. For some reason, females do not like to share spaces & people with other females! So, a neutered male, from your local shelter, would be great for her.......Someone to play with & tire her out! Besides, two cats playing is more fun to watch and they get into less trouble........
Hope some of this helps you.......Don't give up on her, she just has some behavior "issues", that can be corrected, if handled with patience & a LOT of attention............Good luck.....