DP back in contact with old female friend

[TheFirmPanda]

Just that really, DP back in contact with old female friend he knew 15 years ago. We have been together for 13 years, he stopped talking to her around the time we got together, they met on an online dating app 13 years ago, they weren't attracted to eachother and were just friends, hung out as friends only, never slept together or kissed etc. Just friends with similar interests. The friendship kind of fizzled out after a year of us being together, but now he's gotten back in contact with her, should I be concerned?

So did he tell you he was back in contact with her?
Has he met up with her?

They were friends before you met. Are you threatened of her?

Do they have a niche shared interest?

If not then it seems a bit random. Who initiated the contact? Was it via social media or phone number?

so he met them when he met you, it fizzled out now he’s gone back to them…
assume it’s your dp who says they weren’t attracted to them…

YANBU

More context needed

they met on an online dating app 13 years ago, they weren't attracted to eachother and were just friends, hung out as friends only, never slept together or kissed etc.

is he your only source for this account?