hi krusty,
i think your little girl has become a woman, it's always good to get a second opinion so let's see what bruce has to say. the second picture is kind of strange but i think it's a weird angle, is this a different picture of the same horse? i have a small juvi h. comes who takes on a rather strange pear shape when she's gravid, scared me the first time it happened.
you mentioned that "she does appear bloated and then it goes away" - this is probably on a pretty regular schedule right? you also may see some swelling/change in color in the area of the ovidepositor during this time, another indication that she is with eggs. they'll generally do two things with them if they don't have a mate to deposit them in, either reabsorb them or expell them. as bruce mentioned, if she does drop them you might see little orangish eggs in the tank.
this works for lighter colored horses but you can try it: shine a flashlight at her side when the lights are off (from behind), you can actually see the orangish color of the eggs in her abdomen.
it's good to hear that she eats, swims, and is acting normally. if anything changes there give a shout.
nonna - why don't you post a picture in a new thread here or as was mentioned seahorse.org? i have to plug renee (seahorsedreams) who put together a great gallery with short write ups on each condition called "Disease Pictures".
ETA: if you go to the org and look in "Disease Pictures" under swelling/bloating there is a picture of a small female i had last year (A-5). that photo was actually taken when the swelling was decreasing, she had gotten quite a bit larger than that

she stopped eating, hitched low and wouldn't move for days. her respiration was extremely shallow and dropped to very, very low breaths per minute. i was able to get the infection undercontrol after starting her on a course of oral baytril and she "shrank" back to her normal size. while she did recover from the infection i believe i waited too long to tube feed her and she never regained the will to eat on her own. i wanted you to see that krusty and know the symptoms she presented, quite a bit different from a normal gravid female, behavior wise.
bruce - i've had problems when i use diamox at full dosage with this particular species, i've used it twice and the h. comes don't tolerate it well at all.