If someone says make them an offer how do you know what's a nice price to offer them for baby girl clothes and stuff?

I'm a single mom to be and I'm only 22 years old. One of the girls I work with told me she's selling a bunch of kid stuff and I asked how much and she told me to make her an offer. It's stuff like crib sheets, a change table, tonnes of clothes until like 2T, carriers like wraps and traditional baby carriers. She said to just make her an offer but I don't know what's even ok to offer her. The stuff is in diaper boxes and she has like ten boxes of girl clothes packed up already. Everything is in really good condition and from places like Carter's and Gymboree and she doesn't smoke or have pets. Like some of the stuff is brand new even with tags.

I'm 5 months pregnant but it's definitely a surprise and it's just me and my aunt and she can't pay for much. When she says make her an offer, what do you think would be ok? Like is it even on me to be like I don't even know what to offer you but what can I pay you?