Acting indifferent, how should I do it?

Well, I'm the person with the "confused and shattered" question a few days ago. As of now its in break mode. I'm feeling better right now. I've been getting a lot of support from my mom and some by my aunt. They both told me and I thought of acting indifferent with my girlfriend. She's been asking me questions on the phone of what are you doing, where did you etc. I've been giving her kind of lackluster remarks. Give the question, "Why do you want to know? " and she answers "Because I just want to know". Right. That makes sense. You want a break but want to know I'm doing. Now they said as mentioned earlier to act indifferent because that could drive her crazy, and might work on my side(I hope). I'm guessing by not giving straight answers and asking if she wants to call me and I say "you don't have to/not necessary". Seem like a start. I want to know what would be good ideas and things to say to show I'm acting indifferent. But I don't want to show that I don't care about her then I might fully lose her and that's a huge no for me, obviously. So if you can give some advice/ideas and/or things to say to her. That would be much appreciated, thanks!