Should I feel bad?

Derquicia
Background story first. A friend/coworker of mine quit the job where we worked last summer to go work for a school. When we worked at the other place, she and I, plus two other girls were in leadership positions. Not only that, we were also really close to each other. I ended up leaving to work at the same school as my friend in December. And after we both left our little alliance between the four of us kind of fell apart. 
Bringing it back to today. The treatment manager, who was one of the members of our group asked me to come back for the summer. I said yes because I needed the extra money. She didn't ask the other girl to come back. I kind of feel bad that I was asked and she wasn't, mainly because I know it will feel like a slap in the face to her. But should I feel bad? Because I do, and I want to tell her before she hears it from someone else. What do I do??

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