For instance she came into our office and said have a nice weekend buy to one of the girls but totally didn’t see that I was there.
Sounds kind of manipulative to me. Passive aggressive.
I don’t know we do talk but she just doesn’t like me I guess.
It just occurred to me why she must be upset with me this time more so.
Why do you think she does not like you? Maybe she just missed you.
Because it’s an office of two people she can’t miss me. She saw me and said buy to her friend.
Maybe say hello next time and if she does not say back to you or you feel that it’s not the way she behaves then ask her in a polite way 'If she is al right?" You are concerned because you value the the friendship\relationship\work and it is necessary to clear any tension so that we could smoothly work. Please do it when she is not busy or she is having a little break (tea\coffee\smoke break). Just ask in a friendly way.
If you feel that it’s some part of your illness then perhaps elaborate this to some person whom you trust.