Five minutes is a bit too long, it could lead to being stressed out and rips and tears of the fins. Flaring is a healthy exercise for the fins, also you can enjoy their beauty for a few seconds everyday, I would plop the mirror in for about 10 seconds tops.
Also no to any other fish friends in a 2.5 gallon, even though you're only get one, still no. Fish friends can be introduced if you have a 10 gallon tank or bigger. I wouldn't get any snails either, Apple/Mystery snails are the most common snails you'll find at pet stores, they grow huge and they poop a lot. Nerite snails are fine I guess, they're great algae eaters, unable to reproduce in freshwater and also stay small. If you want a bottom feeder maybe a few ghost shrimps, but shrimps usually end up as snacks, unless you provide hiding places.
Along with that, I wouldn't get an Amazon Sword, simply because they get huge, and you probably don't have the correct lighting for them to thrive in. Just get moss balls, they're entertaining and fun. ;P