K.,
All babies are different, but my sister-in-law who is a speech therapist tells me that everyone who wants to can get a free evaluation for their children up until age 3. She did it for her own kids just to be sure they were developing on track. It's free & hopefully will give you peace of mine or the resources you need if there is a delay. This website should have a link/info to who to contact in your area. http://www.childandfamilyconnections.org/
My own son is 18 mos. old. He rolled over early & moved around quite a bit (he's still very very active). He crawled at 6 mos. & he pulled himself up to standing holding on to furniture at 7 mos. He never really sat up unassisted until he was much much older. I figured he could do it b/c he didn't topple over when I put him in a sitting position, but then again, he NEVER stayed put long enough for me to really know for sure. Honestly, my head is too foggy from all the sleep deprivation to remember when I knew for certain he could sit up unassisted, but just seemed to be choosing not to do it. Then for a long long time, he could "walk" or cruise holding onto stuff. Around 1 year or so, we saw him take maybe a step or so unassisted, but he preferred to crawl. Actually, he "walked" on his knees. We called it knee-walking. It was the weirdest thing, but he was REALLY REALLY fast. Eventually at about 14 1/2 mos. he began normal walking quite a bit & by 15 mos. the knee walking disappeared almost completely. I suspect that his poor knees getting scraped up outside when he was wearing shorts might have been a motivating factor! We found that our son preferred
to push chairs, the laundry basket, etc. around more than any kind of walking toy. We have one that he stands behind to push & a toy shopping cart too. He probably pushes them around more now than when he first started standing up! Another mom I know has a daughter who sat up on her own, but NEVER crawled. She's a tiny little thing & didn't start walking until she was waaaay over a year old. Now she walks just fine. She wasn't very active early on, but she's got incredible language skills. My son on the other hand, has been moving & exploring for a long time. He's just now starting to talk more. They are all so different & unique, but why not get the free evaluation just to give yourself some peace of mind. You don't say where you live, but in my town there's children's programs where they teach you ways to play with your kids to help them develop skills they need. Not that the staff at those places are complete experts, but they do see enough kids all the time that they might be able to tell you if they think something is wrong & also give you good ideas of ways to help your daughter learn new skills.