When someone offers and then…

Last week one of the mom’s from daycare I’m getting to know offered to pass down her toddler’s son clothes. She said she’d rather give it to someone who needs them than selling them. So regardless, I followed my husband’s advice to ask and offer to pay. I was about to hand her a 20 and she declined but said, when we go out for drinks I can pick up the tab. I was a bit surprised she said that, considering but said ok! So my question is even though she said she’d pass them down and making the last comment, doesn’t this feel like “IOU”. There’s a catch- type?