I'm a 23 y.o. female, weigh 53 kg and can see/feel my heartbeat in my abdomen. should i get it checked out?

Normal usually: There are is rare genetic disorder that affects some and usually the family history of ruptured aorta gives it a way (marfan syndrome). But most people who are thin can feel the pulsations of the aorta no big deal.

No: That's exactly what would be expected. The pulsation from the abdominal aorta is normally visible in thin people. Moreover, an aneurysm (the pathological cause of a visible pulsation) doesn't occur in your age group.

Probably not: Because you are thin, you are most likely seeing and feeling the normal pulsation of your aorta. Unless this is something new, it probably does not need further evaluation.