Reddit reviews Harrison's Adult Lifetime Super Fine 1lb

I'm not sure on that, i've introduced younger birds to older ones and they've went on fine, but I really don't have that much experience to answer your question.

Only suggestion that I will throw is try to change her diet. I see her food bowl has only seeds, which is not healthy. Pellet food like this is best for them and if you can have them eat green veggies like spinach it would be awesome. Note that changing the diet of an already mature bird will probably take some time as they will refuse to eat anything else than seeds. You can search online for how to switch to a different diet.

Also checkout /r/parrots, lots of information there and I think there's more people there. A lot of the advice for other bird usually can apply to parakeets as well.

Good luck!

https://www.amazon.ca/dp/B0041BTI66/ref=cm_sw_r_cp_apa_i_WvDBDbX5DVA3B