Toa Payoh is one MRT stop away from Novena, and it's full of shops including a Fairprice supermarket. There's a
condo near the station called Oleander Towers with 3 bedroom/2 bath ~107 square meter apartments listed at about S$3400/month right now. It's a short walk from station Exit D, mostly covered from the rain from the looks of it. (Check it out on the ground, obviously.) There are some nice HDB parks there, too -- a great spot for your 3 year old to play and to meet other kids, mostly local Singaporean kids. I see about 4 preschools also short walks from Oleander Towers.
Near Bishan MRT -- 3 stops away from Novena -- there's a condo called Bishan 8 that I'd also check out on the ground. I don't see a preschool particularly nearby, so in that case it might make sense to arrange preschool near the workplace. But there's plenty of shopping there, including a large mall (Junction 8), a large playground/park, and a public library. Bishan has two MRT lines, so it's very well connected in transport terms. It's a little more expensive -- up around S$3800/month for a 3 bedroom, it looks like.
I would also take a look at the exact workplace location and bus routes to/from the workplace. If she's not going to be working particularly near Novena MRT station then the two examples above probably get less attractive, although they still might be well connected by bus.