Should I replace the water heater?

[Grey Stone]

Tenant keeps making complaints and is annoying the crap out of me. This is for an older home with approx 1,300 sqft and 1 bathroom with 6 people living in it. When I bought the home it had a 25 gal water heater and we upgraded it to a 50 gallon water heater. And now the tenant is requesting a bigger one. She says it is not adequate for their family size. I'm not sure if I'm being a slumlord or if I have a legitimate reason to be annoyed. Am I legally or ethically compelled to get a bigger water heater? Let me know what you think. What would you do?