Seen this case in the local news and have been intrigued by it, so just thought I'd share some information and thoughts regarding to it.
Firstly a map of the area, I've identified the position of the point where the CCTV footage was taken by the red circle.
So on the CCTV footage Katie is clearly walking down past the side of the buildings (which would have all been closed due to current lockdown restrictions here in the UK) towards the beach and the car park at the back.
Timeline - February 10th
3:48pm - Time of CCTV footage
around 4:14pm - Last spotted close to Pleasure Island
approx. 4:27pm - Drone footage shows a figure walking down the beach towards the water, close to South Promenade
I also noted she appeared to be carrying a handbag (?) in her right hand and something in her left hand (someone already pointed out this likely to be her phone?). The walk from the crossing on the CCTV footage towards the beach is only a short walk (only a few minutes) so it seems likely that she either went back to her car, if it was parked out back there, or just continued to stay around that general area. The last spotting some 26 minutes later seems to suggest she didn't head straight down towards the beach and water, at least not immediately (if we are to believe the drone footage is her).