1993 Chevy S-10 1993 Chevy Blazer S-10 no start

Engine problem
1993 Chevy S-10 Engine Size unknown Four Wheel Drive Automatic 000000 miles

my gf has a 1993 chevrolet s10 blazer, it has some high miles on it, right now its dead, wont turn over. Before it went tits on her, it was getting progessivley harder and harder to turn over, sometimes taking a full 5-10 seconds before firing up. A while back she started it up and it ran for a few seconds (according to her story) before shutting off and refusing to start. Ive tested it myself since then, the fuel pump engages and the battery shouldnt be bad or anything, it may have a low charge from her trying to start it a few times, but when I turn the key, the engine tries to turn over, you can hear it cranking but no luck, the lights go dim and now with the battery lower it just goes click and nothing, no sound, dead battery for that, but before it cranked but would not turn over, and ideas? Personally I think the starter is dead, but then why would it run for a bit before shutting off and not starting anymore