My sister is a player on Sylestia her username is lydiagrace217 and she is really struggling to get back in her feet after running out of gold purchasing a third party slot. She cant beat the level she is on and cant seem to sell her pets. So Im going to help out Im selling pets in my hatchery for 1,000 each!! If you dont want to purchase but still want to help message her and let her know!! This will really mean a lot to her! Thank you guys!!

My stables and hatchery are too full or I'd probably try to help. But when my sister started playing I don't even know how she got so much gold. Maybe it was because of the Oopsie eggs. Also, well, she took several tries to beat Cereth and his bandits.
A good idea for earning gold is doing missions, so perhaps your sister should try that. Selling items is also a good choice. And you can try lending her some of your gold.

Thank you!! I will let her know!!

My sister started a few days ago, too. :) It's been very helpful. We also kind of help each other. She needed Egg #9, I need eggs #2 and #6, so we traded. You can try that too.