My 9 week old has been swaddled with a blanket across her waist tucked in. Recently, she has been wriggling up the bassinet with her head touching the head of the bassinet, along with her arms out of the swaddle. I found her last night with her arms out and sucking her thumb. Should I still be using a swaddle? She hasn't rolled yet but has been good with keeping her head elevated for a couple of minutes with tummy time, and forcefully pushes her legs into a standing position during the day. How can I keep her comfortable and safe?

It is not unusual for baby to be wriggling around in the bassinet.
Some babies do not respond well to wrapping/swaddling & prefer to have their arms free.         
Some babies like to touch their face or suck fingers or thumb when settling.

You could try settling her without any swaddle, or wrap with her arms out. (as for 3 mth old)
https://rednose.org.au/article/wrapping-babies

Most babies do not roll to tummy intentionally before 3 months; however, some babies do roll, especially to the side or other parts the cot, at a very early age. This is not unusual.
There is no need to stop your baby from wriggling & changing her position, but it is important to make her environment safe in light of what she is doing.
Often this can mean that baby is soon going to be rolling, so it would be safer now, to treat her as if she is attempting to roll.

Most babies will be rolling over by 4-5 months…....some earlier, some later.
This is very normal as babies grow & become stronger many babies then prefer to sleep on their tummy &/or side.
Once rolling or attempting to roll the following is important:
*Time to stop swaddling/wrapping.
*It is important that you move her from bassinet to her cot once rolling.
*Baby needs arms free & the space of the cot to roll safely.

Once she is rolling it is important to make the environment as safe as possible for this to occur.
Continue to place baby on the back to sleep.
Ensure cot mattress is firm, well-fitting & flat.
Ensure there is nothing loose or soft in the cot.
Preferable to use a sleeping bag when rolling that has appropriate size neck & arm holes, rather than swaddle.

Red Nose has the following information when baby is rolling.
Give baby extra tummy time to play when awake and supervised as this helps baby to develop stronger neck and upper body muscles which in turn enables them to roll back over.
Make sure that baby is on a firm and well-fitting mattress that is flat (not tilted or elevated).
Make sure that baby’s face and head remains uncovered (do not use lambswool, doonas, pillows, cot bumpers or soft toys)

As babies grow and develop they become very active and learn to roll around the cot.
At this time, continue to put them on the back at the start of sleep time, but let them find their own position of comfort.
By this stage it is not necessary to wake during the night to turn baby over to the back position

*Do not use any devices designed to keep baby in a particular sleep position.
https://rednose.com.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over