How to maneuver?

Offered a nonfinance internship relevant to ultimate career goal. I was asked to reply in a few days, and I need to apply for summer funding before Feb anyway.

Got an interview but it says its superday is late jan/early feb (either way later than the deadline by which I need to reply to the first one). What should I do? During the interview for the first internship the interviewer said she wanted to make sure I'm definitely coming because she didn't want to hold me a spot (because she's considering my app a few months early anyway) if I'm not coming

Stall the nonfinance internship, ask for an extension ("will almost certainly accept by mid-feb, just wanted to figure out funding & housing before I accept")?