Is he starter the problem

[szap]

A coupkle days ago my sister's Genesis would not start, She was able to jump start it and, as in a few other posts, it would start until it wasn't driven for a extended period and then it would be dead again.. Jump starting has always worked. She took it in to a local Meineke and they replaced the battery. A couple days later she had the same issue with the car not starting. She jumped it and took it back to Meineke and they supposedly did some diagnostics and told her the starter was bad. Is this possibly causing the problem and, if it is, why does jump starting it work? I am no mechanic, but it seems to me that if the starter was bad, jumping the car would not work. Is the starter somehow draing the battery? Thanks for any advice.