You're here now asking for advice on what happened, a post-mortem so to speak, yet you were getting plenty of advice in real time which you kind of ignored, brushed off, or had the attitude you were going at your own pace and knew what you were doing.
Go back and read your last two threads over the last 2.5 months since you met neighbor lady. People recommended: don't spend too much time together initially, don't over pursue, set fun dates, escalate the physical aspect, and stay out of the friend zone...etc.
You were in her house to make dinner and drink two bottles of wine and didn't pursue to the opportunity which means either she wasn't feeling it or you weren't acting confident and gave off friend vibes.
Now you're thinking about her and how she ghosted you and lamenting the loss of a relationship when you two hadn't even kissed (peck on the cheek doesn't count). Instead, fill up your time meeting new friends and new activities. "Darts and minor stuff" doesn't sound too significant. Grand kid time is great, but not exactly getting you out there.
IMO let neighbor lady go for the present. When you come back in 2-3 months if your paths cross then flirt a bit and ask her out on a date with clear intentions to be romantic, not friends.
Me:39 Ex-W:37 M:7 T: 9 S:6 D:3 BD/IHS/Confirm EA/PA: Feb '20 OM1 affair ends: May '20 W/OM2 & moves out: June-July '20 W files for D: Jul20 OM2 confirmed: 9/2020 Divorced: May '21
