iPhone screen glitches out and touch functionality stops working?

Hey! My sister has an iphone that the screen starts showing all these crazy lines and it will stop accepting touch functionality similar to the one found in this image,[http://Picture|https://2.bp.blogspot.com/-ZhVolzE1GD0/V...]

However I can't really seem to find any solid solutions to this besides ask apple for a new phone, any ideas on what parts might need to be replaced? I have a bit of a background doing chromebook repairs for my school but I have never really had to troubleshoot a iphone before and I don't want to buy a bunch of parts I don't need.