Exersaucer is your answer! My kids LOVED that thing. But, just to let you know, my son was sitting up on his own at 4 1/2 months, crawling by 5 1/5 months and walking at 9 months. So, you may want to spend some time on the floor with your little one and let her sit with a boppy pillow behind her in case she falls over. This will allow her to practice sitting up on her own. Or, you could sit behind her, letting her lean on you and hand her toys from the floor. Showing her that they are there may help her to figure it out.
But, as mentioned before, to give you a break so you don't have to be there every second, the exersaucer will let her sit/stand and play by herself. Good luck!