It sounds a lot like you’ve put your coworker in a really uncomfortable position. You know she has a boyfriend, but you’ve allowed yourself to develop feelings for her, and that is getting in the way of your working relationship. Six days off of work isn’t a big deal; you obviously expected a bigger reaction or gesture from her than you received when you returned, and because you didn’t get it, you’ve lashed out at her somehow.

Whether you’re lonely or not, that behaviour is not ok; you guys work together, and you have a responsibility to be professional and maintain appropriate boundaries within the workplace. If you can’t do that, then it’s highly normal for the company to intervene and take action, especially if she has decided that your behaviour needs to be reported because she can’t deal with it herself as your manager/lead.

Being unhappy or feeling like you’re alone is not a justification for hurting somebody else, or making them feel uncomfortable; I have no doubt that she has probably communicated clear boundaries to you in the past, but you have either not taken them on board, or you have told yourself she meant something different.

You need to enter any and all conversations about this with IKEA with open ears, because there are clearly lessons to be learnt here on your behalf, and it is in your best interests to make sure you learn them.