I would burn this tree ASAP. It is infested with several kinds of scale. Your friend needs to learn about citrus scale and how to control it. The tree looks beyond saving to me.

The Fruitnut

Looks to me like two problems: poorly draining soil causing root rot. Citrus must have soil that drains fast, like pour in some water to the pot and it disappears in a few seconds. The cottony cushion scale/other scale can be gotten rid of easily with dormant oil. Looks like the tree is doomed due to no healthy roots left!

Here is a link that might be useful: mrtexas

Kind of looks like the tree has a case of aphids also, which is helping to attract the lady bugs.

Just doesn't look good. My first thought when I saw the leaves was severe root rot, you might even be able to lift the tree out of the soil--doubt there are many roots left.

Might be better to get rid of the tree--looks like a goner anyway, eliminate the scale and aphids from all the plants around the area, then get another tree.