Her Whole World - Michelle Hall

Having fallen out of touch fourteen years prior, single mom Madison Kahn reunites with her college best friend, Harrison Daniels. Just as their reunion quickly heats up, a phone call throws their spark – and their planned summer together - into jeopardy.
She learns her mother's mental health has landed her back in a psychiatric ward. After a visit to the hospital, Madison realizes she can't allow her mother to return home alone, and so like countless times before, this burden falls upon her. Though no matter what happens, Madison tells herself not only will she not lose Harrison again, but she'll make their time together absolutely unforgettable. But with an ex-husband intent on reconciliation and a daughter bouncing between summer camp and home, Madison's summer and her newfound romance with Harrison may just topple, along with her own sanity as well.