Is there a web interface that can easily be used with most APIs?

I'm not sure where to ask this. My friend uses AI a ton for work and is constantly juggling between ChatGPT, Claude, Perplexity, and now DeepSeek. She's paying subscriptions for all of them. I tend to always have extra API credits. Is there a service that offers just the web interface so she could sign in, use my API keys, and easily switch between models?