urgent house training help needed

I adopted a 2 year old female dog around 2 months ago. I am having trouble house training her; specifically when I leave the house.
   
To elaborate, I have no problems with her when we are at home, but when i leave her unattended for a couple of hours (alone) she pees inside the house. I don not have a problem with her pooping or peeing when i am around rather when i leave her alone.
   
to explain her usual day: I walk her at 730 AM, drop her to my parents house till 4 (1 good meal at 1 with a small 10 min walk after), she is dropped back to my place via my roommate at 4... i then walk her at around 6.
   
she sometimes pees at my parents place as well but not a majour issue , my main problem is to solve the peeing when i leave her alone
   
PLEASE HELP ME I TRIED EVERYTHING from telling her no then taking her downstairs, screaming (gets her nervous and she pees herself), long walks before i go out .....
   
just a note (she know what she did is wrong when i get back home and she refuses to come to me when i call her)