Bid farewell to my ex without telling my new girl (a moral balancing act)?

Anonymous
For context I'm an expat living in a foreign country, last year I started dating a fellow expat from my home country and things went good for a while until she left me because she was dealing with a lot of mental stress and conflicting feelings. We stayed friends.
A while back she told us (we have friends in common) that she was leaving and moving back home and couldn't deal with the expat life anymore, so a friend threw her a farewell party.
I'm now seeing a girl (a local) and I didn't tell her what the party was about but went anyway. Me and my ex bonded very well, reminding us of the good old days. We both got drunk and put arms around eachother when standing in the cold but I made sure nothing else happened.
I accompanied her home since she lives near me and bid her goodnight and farewell to which she replied with a kiss on the cheek.

While I do feel like I handled it the best way possible without putting my current relationship at risk but at the same time remaining faithful to my girl I do feel a bit of a conflict.
While it's an unfair comparison it does seem the chemistry I shared with the ex is much stronger and always came so naturally so seeing my girl tomorrow might seem strange as my brain will be drawing comparisons. While I had fully moved on this event definitely put some things in a new (or old) perspective and I do not want it to linger and bleed onto my current attempt at a relationship.
Bid farewell to my ex without telling my new girl (a moral balancing act)?
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