Have you tried pushing or feeding until sleepy but not asleep and putting in cot then?
Does she sleep in her pushchair at around the same time most days?
When you put her down at night do you have the same routine - same person, bath or story or song or whatever?
If it were me (and please ignore all or anything that doesn't suit you) I'd do the following:
If she's sleepy this afternoon, feed her until sleepy, and put her in her cot, staying and patting/picking up/whatever soothes her to sleep.
Bedtime I've always done bath, milk, story, teeth, song, but whatever works for you. Feed again until sleepy. Put in cot, do the shush/pat/whatever until she sleeps.
When/if she wakes, leave for 5 mins to see if she settles. Then go in again and calm her down preferably without picking her up. Offer more milk if needed.
Next time, wait a little longer, say 7 minutes. This time just pat.
10 mins, next time, checking she's not super distressed. 10 mins each time after.
You and DH sleep downstairs.
Tomorrow morning make sure she's up reasonably early (before 8)
At 10ish put her down as per nap today. Wake at 11.
At 1.30ish put her down for nap. Don't let her sleep past 3.30.
Make sure she does something fairly active in the morning and the afternoon, but nothing too exciting after dinner.
As I said, that's just what I'd do. I'm no supernanny or sleep consultant or whatever.