With her being alone she should be ok in there for a bit in that tank. You will want to upgrade her to a bigger home in probably 4 - 6 months. The good news is you can then use this tank to grow plant clippings from you pruning

You will want at least 10g of room for her. Personally I would get her a 18x18x24 Eco terra

When frogs get "fat" they get rolls of skin above thief shoulders and around their "ears" just keep doing what you are doing and she will be perfect