Hello, Paul. SV is a paniculata and paniculatas can withstand a lot of sun in the northern half of the country. It should bloom well if you can provide more than 4 hours of sun during the summer months.

Your mother can try to acidify the soil to change the macrophylla to blue. It is a slow process that takes a while. It requires applying acidifying amendments regularly (iron sulfate, aluminum sulfate, garden Sulphur, green sand, iron chelated liquid compounds, etc) in order to lower the soil pH. It is easier done with potted hydrangeas but lots of people still do it.

A macrophylla hydrangea from the Endless Summer Series, Forever and Ever Series, etc may bloom better in your mother's garden. Of course, if the selected one is a colored hydrangea, it will bloom pink unless you amend the soil. You could also try winter protection techniques.

Luis