Baby sits up while breastfeeding

11 month old just learned how to sit from a lying position.

When it’s nap time, I lay her down to nurse.. and previously she would fall asleep while feeding.

Now she will nurse a bit and then sit up even though she is exhausted and rubbing her eyes. I drag her back and give her the boob to nurse her again but this cycle keeps going and is exhausting!

Any ideas of how to tackle this ? Also looking for reassurance that this is completely normal and just a phase!!