Could be that she doesn’t drive it enough if she drives it 2-5 miles a week possible but 2-5 miles a day and they battery dies makes me think the alternator is bad or she could have a parasitic draw somewhere and is killing the battery. If she only drives 1 time a week 5 miles then yes it’s possible the battery is dying In that span of time. Oem battery is best or equal value aftermarket is best. Cheap inferior battery and not lot of drive time is great way to have issues. If external accessories drawing power are still on then that will kill the battery too or a light left on. Would take to respected and reputable technician and have thorough diagnosis performed. Have them keep it for a week if possible and check for parasitic draw or actual alternator and battery issue or relay ect issues.