Agnes, I may be wrong, but think the two cheapest ice rental rates for indoor rinks in the DC Metro area are Bowie and Fort Dupont. (I'm not sure about Dale City or Piney Orchard.) If I remember right Bowie was around $250/hr, but you'd have to call.
A lot of rinks offer cheaper rates after hours (e.g., after they normally close). Maybe she can try then?
Unfortunately, in VA, there aren't all that many rinks, and traffic is very bad, giving them a captive market, so they can charge what they like. Reston has some daytime freestyle sessions where almost no one skates - maybe worth a check. And Piney Orchard and Bowie (maybe others too?) have some early morning freestyles and daytime publics that are sometimes empty.
All everyone really needs is a rink of their own.
Which rink was it? I wasn't aware anything in the area would charge $1000. I'd heard of $350 at one of the more expensive rinks, but... Maybe she wanted something on short notice, so they would have had to cancel something else.