That's a lot of amphetamine to start with..I'm sorry for you gf, I hope things will get better.
I remember first time it was like a small line..and It was making me euphoric for like 10 hours straight without accusing hunger or sleep. I did like 1-2 lines everytime I was using it (kinda like once a month, something like, when a festival occured) and that was enough for me, maybe too much, when I was coming home I still had eyes wide open and no hunger at all. And I remember those times when one single line could give me almost the same effect of the E, at least for the first 30min-1h.
Then I started to work and other problems came in my life, not to mention depression and boredom, so the assumption increased by a lot, it was not anymore the "party drug" u take sometimes when u go to the club, it was like my breakfast.
Now I don't feel anymore the "mdma rush" when I take it, I don't even feel euphoric. It's just a little slap on my face so I don't look sleepy. I can even eat and sleep after taking it..what a joke don't u think? Now I'm reducing it slowly, because I want it to be again an occasional party drug, not my breakfast. And I don't want to abuse it anyway.
So take a break, don't abuse and you will be fine. And if you really want to test something new, start with small doses and wait some time for the effect, don't be impatient
Best Luck!