You need a thermometer - so buy one since your current one doesn't work - otherwise your axolotl will get stressed, if she isn't already, can develop fungus and/or will get sick.
As for water testing - if you don't have the test kits - take a sample of tankwater to your petshop and ask them to test for ammonia, nitrites and nitrates and record the figures. Basically if ammonia or nitrItes are over 0 you need to do frequent partial waterchanges (20-30% only).
What is that dark thing in the second photo?
Does she have any hides/caves? -If not add at least one or partially cover her tank so she has somewhere to retreat.
Other foods you can use are = garden slaters (woodlice), snails (break the shells before adding) or slugs - just make sure that pesticides aren't used in the garden. Also, frozen bloodworm cube - thaw the cube and give it a rinse before dropping it in the tank. And another alternative food which should only be fed occasionally but might help fatten her up a bit are wormlike strips of red meat (liver, heart, steak, snitzel).