I know you're scared for your aunt. It's really hard being so far away and feling helpless. It's your aunt's decision, ultimately, whether she decides to get treatment or not, though I'm sure you wish you could make her somehow. Sometimes it takes a lot for people to realize that things are out of their control, and your aunt probably has trouble admitting that to her self and asking for help. Is there any way you can write her a letter and let her know that you care and are worried for her? Maybe knowing how hard it is on you, watching this happen from afar, will wake her up a little bit.
There may come a time in her swing that she realizes she needs help. When I'm manic I don't even stop to think... just don't give up hope that when she's feeling differently, she may get help on her own.
*Sending you hope*