Hello Llv, thanks for coming to the site.
What you have told us must be so disappointing for you and even though it's been only a few days to you, it's a long time to try and cope with what's been happening.
For this to leave you struggling at home, made you quit your job and has disrupted your daily life where you are barely looking after yourself means a decision needs to be made regarding whether or not you want to pursue her relationship.
With all the ongoing remarks made to her by other people, she may believe them if they are offering other incentives that she believes may come true, which may be completely different in your current situation.
I can't tell you what to do, but having her in the next room with somebody else should stop, either saying it's not going to happen or telling her that you can't let this happen, she needs to make a decision it's either being with you or with them.
Whether she has changed because of them means that doesn't have the sympathy for you at the moment, which isn't your fault but only cares for whatever else she has been promised.
Please remember there are other people out there who would be willing to have you as a close friend but you will need someone who is capable of convincing you this, so please keep posting on here and can I suggest you also see your doctor.
We want to help you overcome this.