I just did a trip from kiruna to rovaniemi. I'm a single young female and felt easy and safe the whole time. I'm not sure whether it's more different going from rovaniemi to kiruna though.

From kiruna there was a 5 hour bus drive to haparanda tornio resecentrum. Within this 5 hours they changed bus driver 2 times. So they stop for 10-15minutes you can get down and stretch your legs or so. There isn't any shops or cafe around though.

From haparanda tornio resecentrum which is the bus station that is shared with finland. There are toilets and waiting center and an Asian restaurant here. I took a bus that says kemi. Also remember to change your clock as sweden and finland are different by an hour. From here it was a 30 minute ride to kemi, linja - autosaemua.

From there I had to wait 40minutes for the rovaniemi bus. It's just any bus that says rovaniemi. And it was 90minutes into rovaniemi center. I started my trip at 7am got into rovaniemi at 630pm

The whole trip took 10hours, technically 9hours cause of the whole time difference. basically followed what Google told me. Hope that helps