NO. Not in a million years.
Using magic is probably the WORST way to propose. You should never use magic to help your relationship. I too have a girlfriend who also really loves my magic. But i would never mention anything about magic during a date (unless she brings it up). What i'm saying is that you should just be yourself when it comes to relationships, don't try to go overboard. I'm only 15 so i don't know much about proposals but i do that if i were to try to propose to my girlfriend using magic, she would definitely say no.
i must disagree with you on that magicshadow9.
with this type of situation it really depends on the individual you are proposing to. i really don't think members here can give you great ideas on your proposal as none of us here knows your girlfriend better than you.
if your girlfriend loves you and truly wants to be with you she will say yes. even if you go against magicshadow9's advice.
you mentioned that you kind of got her into magic as well? if that really is the case, is she familiar with pk effects? does she know what a pk ring is? if she knows, this might work well.
show her a couple tricks with a real pk ring. then tell her you bough her one as well, but in reality... you have the engagement ring in the pk ring box. when she opens it... you do your thing on the proposal. women likes surprises.
good luck!!!
ps DO NOT USE THE PK RING AS THE ENGAGEMENT RING!!!