I'm sorry, that is definitely inconsiderate. It sounds to me like she is flailing around a little, not sure of what she's doing or wants to do.
I think the dinner out with single, new female (available?) is completely outrageous if she says she wants to reconcile with you. I don't understand where she's coming from with that at all. Did you know about that dinner before you spent the afternoon with her? That would have made me pull completely back.
The co-dependency issues she should discuss with a counselor, or better, the two of you in couples counseling. Maybe there were real issues, and she's trying to get to them. I'd take this seriously and agree to talk about it. Combined with the dinner above, it sounds like she is afraid of being too much a part of a unit and that she somehow has lost herself a little? But doing things separately is not going out with a potential flirt!
The 'when we get back together' sounds to me like she's taking you for granted. I would be tempted to become a lot less available if I were you. I would make very sure she's not envisioning a future in a sort of open relationship.
I can understand not announcing the reconciliation. She was quick to announce the split and the new R with OW, so maybe she learned that it was not a good idea to involve other people in what was going on so quickly. However, the dinner with the friends she trashed you to, would be a great opportunity to tell them that she regrets the things she said and they came out of her own guilt. She doesn't have to say anything about a future R with you.
Just my 2c...
M 16 yrs, WH62, P54 3 adult blended kids EA 11/13, BD1 6/14 PA fall 14, BD2 2/15 Piecing 2015, BD3 12/15 Separated 4/16 WH moved OW in 5/16 Divorced 6/15/17