G.B.
To use the nasal suction device you need to wrap her in a towel or blanket where her arms and legs are confined then hold her head still. You need to learn that if you don't get the snot out it sits in her sinuses and festers, creating puss and green mucus.
The snot has to get out of her head somehow so it drains into her tummy. She can't digest it so it comes out her hiney in her diaper. Yuck...Otherwise it comes out the nose and drains or it comes out the ears and causes an ear infection.
It has to get out, the how is up to you in a way. If you hold her down and suction the snot out she will get better sooner but if you just can't help her that way then the doc can put her on some antibiotics to fight the infection she'll develop.