I'm not asking someone what they want as a present.
Beyond the assertion that every gift should be a surprise, a gift that has care and thought put into it while also being a surprise is an A+ gift but it's surprisingly hard to buy gifts for some people.
Rather than just giving them cash, ask them what they would like. If they say "I don't know", then ask them the same question only more specific, like "What would you really like right now?" or something along those lines
Also OP like I said earlier if you really don't know what to get her, get her a yankee candle. I'm completely loving serious, moms love yankee candles