I know Belfastlibe isn't everyone's cup of tea but I browse every now and then. I stumbled upon this article. To me it looks like a white training flare
https://www.belfastlive.co.uk/news/belfast-news/mystery-surrounds-object-videoed-falling-30125153
That site is full of guff and loads of pop ups,video would not load on my tablet so will try it on Pc later.I lived in that area for over 30 years and departures from BHD would routinely be over that area.
Sounds to me very like a Chinese Lantern,I don't see any reason why a flare would have been fired in the area, the Oval is too far away if it was at a footie game.
I reckon Chinese Lanterns are responsible for loads of UFO sightings as well,even though I think they banned in many countries.
I have seen the clip now, It seems to be part of a contrail at first,I think the problem is the perspective she has viewed this from.
After watching it a few times I think it could be a comet that was visible in UK over the past weekend. Comet A3 (Tsuchinshan-ATLAS)