Is it a good idea to travel 6 states away right now to meet a new niece?

It's not up to you to decide what your friend should do. If you're able and willing to look after the cat, say so, but remind your friend that you won't want to be within Covid distance of them for a week when they come back.

Nope. You can get sick. The virus is out there.

If you're willing to cat sit then do it. Your friend's travel should not be

related to that.

If you even thought to write this question you

1. Need to educate yourself

2. Have someone else take care of the cat because you are going to be freaked out the entire time.

If your friend runs around town without a care in the world, then you shouldn't have much to do with the friend right now.

If your friend takes safety precautions, it doesn't matter if they are in their house or in their siblings house.

If they are driving (actual driving the car part), then they don't need to do anything.

If they stop for a pitstop, gas, food, whatever = they maintain distance (and wear a mask if it's required in the state) =  what's difference about this then at home? home??

If they have to stop at a hotel = big deal, covid does NOT go through HVAC systems, covid does not transmit well via inanimate objects.

If they are flying and the plane is crowded, then my recommendation is 2 masks or a mask and face shield, but planes are not hotbeds of transmission so it does not matter.

Since your friend would not want to get their newborn baby sick or the baby's parents, we can surmise that s/he will take appropriate precautions.  The concept of "we can do it later" for little events like going to a movie make sense to me. 

Holidays/Big events/Once in a lifetime events - NO.  We can get together next year? No. We have no idea what is going to happen to our loved ones or us.

Not according to any of the current advice being offered by any state health dept. official, no. 

If you're dumb.

I wouldn't, but I'm not you. Does it SEEM like a good idea for you?

sure why not, endanger yourself and old people and especially a new born who has literally no immune system right now, we have a vaccine now don't we

No go in the morning 

I guess.