If she is a walker, I wouldn't get a double. We did with our second. First was a walker and was 28 months when the little one came. He got lazy and would rather ride than walk. Not to mention it was HEAVY with the two of them in it. I wore the little one when we really needed the stroller and our first strolled. I love the moby and ergo.
Now we are expecting a third. The second one is NOT a walker so I assume I will be pushing her. I still have a double and may use it a little, but I plan to wear this one and push a single stroller for the most part.
There will be 2yrs 5m between mine and i wasn't planning to get a double stroller unless i find i can't live without one. Figured that the newbie could be carried round in the babybjorn for the first couple of months and was going to try a buggy board for the toddler when it got a bit bigger and had to go in the pram. Which reminds me, i need to do some ebaying!
If you do buy a double stroller i've heard that Phil and Teds are very good, although the bubs always looks a bit neglected slung underneath the pram! But then everyone tells me thats how it goes with second babies :(
When I was 100% set on a double stroller I wanted to go with the "Baby Trend Sit and Stand- Green Tea" It sells at Target and BabiesRUs... around $155-170. LOVED it, the back could be a seat for infant car seat to fit in or a seat for toddler or a standing pad for the oldder child that may walk occationally. The front is only a seat or insert a car seat. It is a great stroller and very durable. The cost isnt bad either.
Reality check we had, our toddlers will be almost 4 by the time we need the stroller, based on seasons... so we found a nice second hand- less than 1yr old individual stroller, car seat and base combo for $90. Couldnt beat it. So in the mean time I have two umbrella strollers ($16 ea) and a set of 3 plastic "munchkin" brand connecters ($8) as our double stroller for our toddlers. Great for the mean time.. but wont work for an infant.
I am getting (second hand from cousin) a Phil & Teds. It converts for double or single and folds down quite small. She swore by it. There was only 14 months between her two. There will be 2yrs 2months between mine. Some people dont like the idea of the baby being tucked down underneath. I like this because people wont be sneezing and coughing all over bub when they want a peek.