Small hot water tank

[Sasha Fukuda]

So, i just rented this apartment of mine. It was previously owned by a slumlord and its had the same inherited tenant in it since I've owned the property. After she left, I renovated it. The new tenant rented it without seeing it first (she was on the other side of the country). Afterwards, she complained that theres not much hot water. The water heater's new, the mixing valve is new, the shower has a water efficient faucet. However, it's only a 30 gallon water heater, so it only provides a hot shower for 15- 20 minutes. On the one hand, I feel bad because she didnt know about this when she chose the apartment. On the other hand, the current water heater fits in a cubby that a larger one wouldn't fit in. If I got a bigger one, I'd just need to have it sitting in the kitchen, which is worse aesthetically. The second thing is, I think plenty of tenants wouldn't mind this, and I dont want to buy another water heater just to satisfy something future tenants wont care about. Rent is currently only $800/ month, so a new water heater would cost roughly a months worth of rent I'm guessing. I could offer to lower rent, let her off the lease if she finds somewhere else, or see if my plumbing company would give me a deal trading one new water heater for another. Thoughts?