Sounds like you're a dick.
Is this a repeating trend, or maybe a once-in-a-while thing? Rather than saying that you want to meet on certain days, maybe just try and put out a general "Hey, I want to spend more time with you." It sounds sillly, I'm sure, but just saying "Hey, I feel kind of neglected recently" is a way to both be direct and show her you're willing to open up.
Asking her if she's avoiding you will instantly put her on the defensive, because that could come across as a 'YOU are doing this to me' statement not a 'This is how I feel' statement. One feels judgemental, the other feels trusting. In any argument, the easiest way to make it escalate it is to use 'you' statements.
It´s a repeating trend...basically the last 2 weeks she mostly told me that she has no time to spend with me cuz her friend told her to hang out...and sure i don´t wanna blame her...i just told her that it feels weird to me when she e.g. replies to my sms really late or not at all...then i asked her if she is avoiding me. I mean last week she told me that she feels sory for neglecting me and told me it´s because of job stress she has...i then said that it´s ok if she needs a bit time to rest...but now it gets more and more frequent and I really feel neglected now.