Do you have a rock climbing wall in your town? Get her a certificate for one session, rental and shoes and equipment. Or a kayak rental.
Get the other an Itunes giftcard, or tickets to a show you both want to see and offer to pay for babysitting that night.
ETA: Urgh, what Hello Again said.
Giftcards suck–they’re just money, but with rules.
For the mom, how about a cool board-game and a CD (gift receipt included in case you strike out). For the other, uhh… bottle of wine? 
This is very close to the route I’m thinking of. The sporty one and I have been talking of trying a rock climbing gym, so I’ve started looking into it, and they have intro sessions for an afternoon for a reasonable amount.
The other, I’d like to find some kind of show/concert, etc to bring her to.
I’ve always been a big fan of the 'even’t gift. Most of us have enough stuff and things already, but won’t always go try something new and fun without being prompted.
As for all the comments that somewhat insultingly suggest I don’t know these women very well - well, I don’t. We’ve become friends in just a couple of months, so we are all still learning about each other, but as none of us have a significant other in our lives this year, and have all recently ended long term relationships, we’ve decided to give each other a good holiday.
Cool! Let us know what you decide and how they like it.
Well that’s very sweet. Good for you (all y’all)!
If you want to have an experience, let me heartily recommend Spa Castle, a 5 story Korean waterspa (bathhouse sounds shady, and spa seems zen-like, and Spa Castle is neither of these) in Queens.
Top floor 1/2- Korean cafeteria restaurant - just the basics, a little expensive but not outrageous
Top floor: open air hot pools with a variety of massage jets that tap on; Japanese hot tub built of special wood; sauna; indoor swim up bar
Middlefloor 1/2 - lounge chairs with tvs, for napping
Middlefloor - saunas with various themes - gold lined sauna, salt lined sauna, colored light sauna, jade lined sauna, ice “sauna”; snack bar & bubble tea stand, expensive salad bar; heated floor & lounge chairs for napping; massage chairs; massage/facial spa area (additional charge)
Bottom floor - gender segregated locker rooms, plus a section of naked-required gender segregated indoor hot tubs, steam rooms, cold pools, and seated Korean-style scrub showers. Also, crazy insane buck-ass naked salt scrub station where you can get whole-body exfoliated within an inch of your life (additional charge of $50 for just the scrub, more for scrub + massage).
On a weekday the base charge is $35, stay as long as you want (open till midnight), bring your own bottled water & lunch – they don’t care. Bring a bathing suit & a towel for the top pool; they issue a uniform which you must wear in the co-ed areas. Warning: very busy on weekends with lots of kids.
New York Times Article
Yelp reviews give helpful walkthroughs of the experience - the haters are funny - OMG old ladies were naked near me OMG
I’ve been a couple of times – a bit of WTF and a bit of a schlep but very awesome and fun.
If you decide to go with Hello Again’s idea, I’d like to be your new female BFF. I’m under 30, nice on occasion and in need of some deep exfoliation.
Sure, I’m not gonna say no to more young ladies wanting to join the band!
Besides, you had me with the Arrested Development referenced user name already 
I’m a single mom (of a girl, age 6) and I am pretty much consumed by my girl, too.
I would like things that she and I can do together, such as a zoo membership or even a set of movie passes at one of those dine and watch places. Once I got a matching scarf set (mine and hers) and we thought it was great!