my company won’t fire the women who’s sexually harassing my boyfriend because she wrote fake doctors notes

Location: Portland Oregon
i work in Portland oregon and work for a smallish company. my boyfriend is 27 and my co worker is 40. recently she was going through a divorce and had made passing comments at my boyfriend that made him uncomfortable. my boyfriend had been polite to her because they also have to work closely. well she took the kindness as flirting. (mind you i’ve seen them interact my boyfriend is always just replying politely) it got
to the point where we decided kindness was maybe too much for her to understand. so we came up with a plan together to be straight forward with her without being too polite. this sent her into a spiral. everytime my boyfriend would simply reply kindly or shut her flirting down she began to take it out on everyone in the store. at one point he did some extra work to get the day done and she ended up crashing out on him saying he stole her job.. n then told my boss he didn’t let her go on a break… (they checked the cameras and this was not true.) rhis became a huge issue and almost costed my boyfriend his job. her anger towards him continued for weeks until it turned back into creepy flirting. she comes in on her days off only when he works. refused to go home early unless he’s not there. she gets in his space to the point where he has to step back and asks her to give him space. she touches him without asking. hes blocked her from his phone cause she was legitimately talking to herself saying she wanted to her leave her husband for him MIND YOU MY BOYFRIEND ISNT RESPONDING. this women is a creep and a stalker. she just recently got a new boyfriend whos only 3 years older than her son…hes 19… anyways ever since she tried lying the company had a large talk with her about how she needs to treat other employees with respect maybe two days later she comes in with a doctors note. that her anxiety is too bad to work except for the days MY BOYFRIEND WORKS. so the company is catering to her fake doctors note. while all this is happening my boyfriend has been telling both my gm and my upper management that she’s been sexually harassing him. they ignored it for months till we decided to bring it to the owner as of a few days ago. at first we thought they would just fire her especially because we had to make cited claims with the days she harassed him but our bosses say that she can sue because of her doctors note…. so their new genius plan is to use my boyfriend as bait till she does something again? as if everything else she’s said and done isnt enough? should we sue too??? please help. what’s our legal grounds?? am i right for thinking my boyfriends sexual harassment is more serious than her fake doctors note anout anxiety ? my boyfriend has been miserable at work and it’s started to effect him at home. please help.